PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819501 (2011) https://doi.org/10.1117/12.906842
This PDF file contains the front matter associated with SPIE Proceedings Volume 8195, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819502 (2011) https://doi.org/10.1117/12.899374
We propose two methods for avoiding misplacement phase error in terahertz reflection timedomain
spectroscopy (THz-RTDS). The absorption signatures of the materials are extracted
directly from the second-order derivative of the phase of the sample beam or the first derivative of
the relative reflectance with respect to frequency. The techniques provide straightforward and fast
solutions to solve the phase-retrieval problem in RTDS.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819503 (2011) https://doi.org/10.1117/12.899381
We numerically studied the terahertz wave generation in
quasi phase matched Gallium Arsenide (QPM-GaAs)
based
on difference frequency generation (DFG) process
between resonating signal and idler waves of the
type-IIphase matched
periodically poled LiNbO3 (PPLN) optical parametric
oscillator (OPO). The optimal GaAs length for maximum
conversion efficiency was obtained considering the wave
propagation loss in the GaAs crystal by adding a loss
term in the coupled wave equations.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819504 (2011) https://doi.org/10.1117/12.899428
The spatiotemporal and spectral characteristics of ultrawide-band terahertz pulses after passing through a Fresnel lens
are studied by using scalar diffraction theory. The simulation shows that the transmitted terahertz waveforms compress
with increasing propagation distance, and the multi-frequency focusing phenomenon at different focal points is
observed. Additionally, the distribution of terahertz fields in planes perpendicular to the axis is also discussed, and it is
found that the diffraction not only induces focusing on axis but also inhibit focusing at off-axis positions. Therefore,
the Fresnel lens may be a useful alternative approach to be a terahertz filter. Moreover, the terahertz pulses travelling as
basic mode of Gaussian beam is discussed in detail.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819505 (2011) https://doi.org/10.1117/12.899430
Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the absorption and dispersion of polycrystalline
α - and γ -glycine in the spectral region 0.5-3.0 THz. The spectra exhibit distinct features in these two crystalline
phases. The observed far-infrared responses are attributed to intermolecular vibrational modes mediated by hydrogen
bonds. We also measure the Raman spectra of the polycrystalline and dissolved glycine in the frequency range 28-3900
cm-1. The results show that all the vibrational modes below 200 cm-1 are nonlocalized but are of a collective (phonon-like)
nature. Furthermore, the temperature dependence of the Raman spectra of α -glycine agrees with the anharmonicity
mechanism of the vibrational potentials.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
L. Jiang, T. Shiino, S. Yamamoto, W. Zhang, Y. F. Liu
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819506 (2011) https://doi.org/10.1117/12.899524
In this paper, we present measured results and theoretical modeling of a 1.5 THz waveguide NbTiN HEB mixer, which is
fabricated by in situ process. The NbTiN HEB mixer with dimensions of 1 μm in width and 0.15 μm in length is
measured to be as low as 570 K in noise temperature (7hν/k) even with a relatively thick NbTiN film (10.8 nm). The
intrinsic mixer noise temperature is 300 K after the correction of the losses of quasi-optical and IF amplifier chain. At the
same time, we adopt an optimized hot spot model to simulate the DC and RF behaviors of the NbTiN HEB mixer by
combining phonon-cooling and diffusion-cooling mechanisms together. The measured and calculated current-voltage
curves are in good agreement. The calculated intrinsic mixer noise temperature is 100 K and IF gain bandwidth is 2.7
GHz at the optimum bias point. The difference between the measured and simulated mixer noise temperature is factor of
3 times, which is probably due to misalignment of quasi-optical RF coupling system and air loss. The calculated and
measured results show the two cooling mechanism work together to lower the noise temperature of the waveguide
NbTiN HEB mixers. The details will be presented in this paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819507 (2011) https://doi.org/10.1117/12.899554
The detector array of THz synthetic aperture imaging system is consists of many individual detectors.
At a specific distance, arranging the curvature of the detector array to match with wavefront can reduce the phase shift.
There is not exist perfect detected object in reality. Given the specification resolution of a system, cut-off frequency is
determined to design the longest baseline and to ensure an efficient coverage of the u-v plane. The shorter of the baseline,
the more influence on u-v spectrum is. To be pointed out, throwing away the high frequency component can improve the
resolution of the object. In this paper, by arranging the detector array to make the curvature of imaging array match with
the wavefront and to throw away the high frequency component when the baselines are lost, the result of research proves
the above way is right.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819508 (2011) https://doi.org/10.1117/12.899577
Acquiring messages from the mail but not destroying the envelope is a big challenge in the
war of intelligence. If one can read the message of the mail when the envelope is closed, he
will benefit from the message asymmetry and be on a good wicket in the competition. In this
paper, we presented a transmitted imaging system using THz time-domain spectroscopy
technology. We applied the system to image the mail inside an envelope by step-scanning
imaging technology. The experimental results show that the THz spectroscopy can image the
mail in an envelope. The words in the paper can be identified easily from the background. We
also present the THz image of a metal blade in the envelope, in which we can see the metal
blade clearly. The results show that it is feasible of THz Time-Domain Spectroscopy Imaging
for mail inspection applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Xin-yi Chen, Jian-bo Wang, Gui-bo Chen, Guan-cheng Sun, Jun Lu
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819509 (2011) https://doi.org/10.1117/12.899578
Frequency selective surface is a monolayer or multilayer 2D periodic
structure which is composed of multiple resonance units scattering by a
two-dimensional periodic array on dielectric layer. FSS can't absorb radio frequency
energy, but can filter the frequency which is therefore applied in microwave technique
or stealth technology. The relative research on curved FSS is relatively scarce since the
curved FSS structure can be obtained only when FSS is attached on the materials
surfaces of curved structures in engineering application. However, curved FSS is
widely applied in practical engineering; therefore, the research on curved FSS structure
has important significance. In this paper, a curved FSS structure model of Y-pore unit is
established and numerical simulated by means of FDTD. The influence of curvature on
FSS transmission characteristics is studied according to the analysis on the changing of
radar cross section (RCS). The results show: the center frequency point of the plane
band pass FSS structure drifts after the curve surface deformation of the structure; the
center frequency point of the curved band pass FSS structure drifts with the changing of
the curvature radius, i. e. with the decreasing of curvature radius, the frequency point
drifts towards high points and the transmittance decreases. The design of FSS radome
demands of accurate and stable center resonance frequency; therefore, the actual
situation of curved surface should be considered in practical engineering application
when band pass FSS is made into frequency selection filtering radome. The curvature
radius should be long enough to avoid center frequency drifting and transmittance
deceasing.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950A (2011) https://doi.org/10.1117/12.900112
The submillimeter (submm) regime, ranging from 100 to 1000um, is an important frequency band for radio astronomy.
A large number of astronomical spectral lines are located in this frequency region. Compared with ground-based observation,
which is limited by the atmospheric absorption of signal, space borne platform provides perfect condition for
submm observation. Here we introduce some preliminary results for a compact 500GHz SIS (Superconductor-
Insulator-Superconductor) heterodyne receiver system developed for future space borne observation. Considering
low power consumption requirement for space applications, we adopt a high critical temperature (Tc) NbN/AlN/NbN
SIS tunnel junction for the mixer, a key component of the receiver system, which may work at relatively high temperature
around 10 K. All the components, including the SIS mixer, HEMT low noise amplifier and optical lens, are assembled
into a compact system. The whole system is cooled by a close-cycled 4K cryo-cooler in laboratory and test result
shows a good noise performance, less than 250K at the 500GHz band. Detailed simulation and experimental results will
be presented in this paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Chun-dong Wang, Hong Su, Jian-pang Zhai, Shi-xing Wang, Zi-yu Chen, Shuang-chen Ruan
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950B (2011) https://doi.org/10.1117/12.900114
4nm single-walled carbon nanotubes ( SWNTs ) of three possible structures were fabricated. The
frequency-domain transmission spectrum of SWNTs was obtained by Fourier transform in terahertz time-domain
spectroscopy (THz-TDS) system. By analyzing the spectrum, we can see that the absorption coefficient of SWNTs
augments with an increase in the frequency. It increases slowly at low frequency, and almost be linear. But after 1.1THz,
the absorption coefficient rises rapidly with the frequency. The result is generally corresponding with the theory
Drude-Lorentz model combined with the Maxwell-Garnett model. But there is some difference at low frequency, further
discuss is needed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Guangqiang Wang, Jianguo Wang, Xuefeng Wang, Changjiang Tong, Xiaoze Li
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950C (2011) https://doi.org/10.1117/12.900120
Interaction between the high temperature (high-Tc) Josephson junctions and 0.14 THz nanosecond pulse has been
numerically investigated in this paper. A general equivalent circuit based on resistively-shunted junction (RSJ) model
was applied to simulate a typical high-Tc Josephson junction under the radiation of 0.14 THz narrow-band pulse with
pulse duration of 2 ns. The varying ratio of phase difference of electron wave functions between the two sides of the
junction, the current-voltage characteristics, and the voltage responses were determined at several specific times during
the interaction. The Shapiro steps were clearly observed but distorted, and then the irradiation frequency was derived,
coinciding with the simulated frequency. Also discussed were the effects of some parameters, including the pulse power,
the normal resistance and the critical current of junction, on the current-voltage characteristics and the voltage responses.
All the results showed that the high-Tc Josephson junctions probably could be used for the direct frequency
measurements of narrow-band terahertz pulses under some specific conditions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Yong Du, Jianjun Liu, Guohui Hao, Changsheng Guo, Zhi Hong
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950D (2011) https://doi.org/10.1117/12.900145
In this work, vibrational properties of a series of parent polycyclic aromatic hydrocarbons (PAHs)
and nitropolycyclic aromatic hydrocarbons (NPAHs) compounds with the substituted nitro group
at different positions have been investigated using terahertz time-domain spectroscopy (THz-TDS)
at room temperature. The experimental results show large difference among absorption spectra of
several NPAHs and their corresponding parent PAHs compounds in 0.1~2.2 THz region, which
probably originated from the difference of NPAHs' molecular structure and lattice vibrational
modes. All the experimental NPAHs vibrational modes showed distinct fingerprint absorption in
THz region. The study indicates that THz-TDS technology can not only give a new experimental
method to identify and analyse such different kinds of NPAHs environmental pollutants, but also
provide a useful suggestion for further assessing the possible relationships between the NPAHs
optical properties and the effects of the substituted nitro group position to better know their
photoreactivity and biochemical activities.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950E (2011) https://doi.org/10.1117/12.900162
A biological sensor based on the resonant transmission characteristics of metal meshes has been proposed in the terahertz
(THz) region. We simulated THz transmission characteristics of two kinds of structure by FDTD method: arrays of
circular hole and rectangular hole. Their resonant frequencies at the interface of metal and air are 1.42THz and 1.225THz
respectively. We find that the refractive index and thickness of the sample commonly affect the surface plasma's resonant
frequency. When coupled with a layer of sample of 50 micron on the metallic meshes, the resonance frequency would
shift to a lower frequency with an increasing refractive index. Sensitivity of two kinds of structure is 0.64 THz/RIU and
0.507 THz/RIU respectively. The sensitivity differences of two kinds of structure lie mainly in the different dominant
resonant transmission mechanism. The thickness also affected detection sensitivity. When thickness of sample is less
than the corresponding resonance wavelength, we need to consider the influence of thickness. This theoretical simulation
can be good reference for the following experiment.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Xiang-qian Chen, Ji-fang Liu, Yan-ling Sun, Lin Ma, Shun-xiang Shi
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950F (2011) https://doi.org/10.1117/12.900171
Terahertz radiation has been studied extensively both experimentally and theoretically within the past decades. A
number of methods have been developed to generate terahertz radiation using ultra-short laser pulses, including
photoconductive effect, optical rectification, and so on. The photoconductive effect has been utilized to generate THz
radiation from a piece of semiconductor with antenna structure. The bias electric field between the electrodes of
photoconductor is limited by the breakdown field of the semiconductor. In order to enhance the THz radiation power, the
distribution of electric field on the surface of the substrate is simulated and the relationship between the geometrical
structure of antenna and bias electric field is analyzed. The results show that the bow-tie antenna works more safely than
other antennas under the same condition, and the breakdown risk of the PC antenna is reduced and the capability of
resistance to voltage is improved.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
J. Y. Chen, J. Q. Liu, F. Q. Liu, L. Li, L. J. Wang, Z. G. Wang
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950G (2011) https://doi.org/10.1117/12.900173
We report the design and fabrication of terahertz quantum cascade lasers at about 3 THz that use semi-insulating
surface-plasmon waveguide for optical mode confinement The single-mode operations are realized by employing
one-dimensional first-order distributed-feedback (DFB) and photonic crystal distributed-feedback (PCDFB) resonators,
respectively. The single-mode operation of up to 88 K and peak power of 9.5 mW at 10 K for the DFB devices is
obtained. The PCDFB devices also emit a single frequency at above 50 K.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950H (2011) https://doi.org/10.1117/12.900179
Light scattering effect can be commonly occurred in the terahertz transmitting spectra of various powders (particle sizes
are average less than 50μm), include pure materials and mixtures. Light scattering of various materials distort
absorption spectra. We demonstrate the effect using mixture of two kinds of powders with different refractive index.
According to the Mie theory, we explain the reason of light scattering effect in subwavelength domain, relying on
refractive index between the powders and their surrounding medium. Furthermore, we show a wavelet method which can
extracts terahertz spectral information without considering scattering effect.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950I (2011) https://doi.org/10.1117/12.900183
In this paper, for explosives classification problem in safety inspection field, feature extraction and recognition from the
radiation data as the core, combined with dual-energy X-ray transmission technology, low-energy forward scatter and
low-energy back scatter technology to get eigenvalue R associated with effective atomic number and eigenvalue L
associated with density. Synthesized R and L, get the discriminate, decision-making plane and distinguish rule based on
the least mistake probability. The distribution of materials with regularity in this plane, there is a curve, most illicit
materials drop into the area under the curve. Then get the criterion to classify the explosives. A given object may be
randomly placed anywhere on the conveyor belt, resulting in a variation in the detected signals. Both an adaptive
modeling technique and least squares method are used to decrease this distance effect. This is the magnitude contribute
for recognition of solid explosive.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950J (2011) https://doi.org/10.1117/12.900188
In material classification, distilling eigenvalue will use the object's true gray levels. The problem is objects in a bag
almost always overlap with others. Being able to identify the object of interest and remove the overlap effects becomes
the key issue that needs to be solved. First, the paper took an n-object-overlapping problem simplified to a
two-object-overlapping problem. So the research focus turned to computing true gray levels for two-object-overlapping
problem. It was necessary to develop models that can be used to remove the background object overlapping effects.
The author took back scatter images for example, discussed the development of the mathematical model for removing
the overlapping effects, solved the model parameter by experiment and analyzed model error. This method has been used
in x-ray security inspection equipment of DT Inspection equipment limited company. The results of application show
that the algorithm is feasible. This is a unique contribution to the explosive detection community.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950K (2011) https://doi.org/10.1117/12.900319
The numerical simulation of terahertz generation and detection in the interaction between femtosecond laser pulse and
photoconductive material has been reported in this paper. The simulation model based on the Drude-Lorentz theory is
used, and takes into account the phenomena that photo-generated electrons and holes are separated by the external bias
field, which is screened by the space-charge field simultaneously. According to the numerical calculation, the terahertz
time-domain waveforms and their Fourier-transformed spectra are presented under different conditions. The simulation
results indicate that terahertz generation and detection properties of photoconductive antennas are largely influenced by
three major factors, including photo-carriers' lifetime, laser pulse width and pump laser power. Finally, a simple model
has been applied to simulate the detected terahertz pulses by photoconductive antennas with various photo-carriers'
lifetimes, and the results show that the detected terahertz spectra are very different from the spectra radiated from the
emitter.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950L (2011) https://doi.org/10.1117/12.900322
In this paper, the low-frequency vibrational modes of crystalline benzoic acid (BA) have been investigated by terahertz
time-domain spectroscopy (THz-TDS) and theoretical simulations based on the linearity combination of atomic orbital
within the Density Functional Theory (DFT) as well as ab initio molecular orbital method at second-order Moller-Plesset
Perturbation Theory (MP2) level for single molecule and dimer. Experimentally, a series of prominent absorption
features of pure benzoic acid relevant to intra- and inter-molecular vibrational modes have been obtained below 4 THz at
room temperature. For the theoretical simulations, geometry-optimization results of bond lengths and dihedral angles in
both BA monomer and dimer are very close to experimental neutron diffraction measurements. Furthermore, the
simulation results demonstrate absorption profile centered at 1.89 THz contains low-frequency modes of Ph-COOH
twisting due to intramolecular motion and cogwheel owing to intermolecular motion. All the intra- and inter-molecular
vibrational modes measured have also been assigned.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950M (2011) https://doi.org/10.1117/12.900323
We have investigated the effect of a moderately strong magnetic field (generated by superconducting coil, up to
380Gauss, 6 quantum fluxes within a single junction; generated by one piece of permanent magnet; generated by two
pieces of permanent magnets respectively) on Nb superconducting tunnel junctions at different temperatures. Both
experimental and numerical results show that the superconducting tunnel junction DC Josephson current can be
significantly reduced by a magnetic field. A relatively strong magnet field may suppress the gap voltage as well as the
sharp nonlinearity at the gap. We also investigated the leakage current and DC Josephson current of the Nb SIS junction
at different temperatures.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950N (2011) https://doi.org/10.1117/12.900329
We present a technique for calibrating spectrum measurement of terahertz time domain spectrometers (THz-TDS) using
absorption lines of carbon monoxide (CO). The mean error between the peak positions measured by our THz-TDS and
JPL database is 3.1 GHz. The results show that CO is suitable for frequency calibration of THz-TDS.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Bihui Hou, Yali Wang, Wei Hao, Guoqing Liu, Bingxin Yang
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950O (2011) https://doi.org/10.1117/12.900330
Promising Crystals of Generating THz have been discussed according as the theory of solid state physics.
We found that PbB4O7 (PTB) crystal has probability of generating about 3.12THz, and Bi4Ge3O12 (BGO)
crystal has probability of generating and 2.7, 3.7, 6.0 and 10.8THz radiation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950P (2011) https://doi.org/10.1117/12.900407
Terahertz time-domain spectroscopy was used to measure the optical properties of ZnO nanoparticles (NPs) in the
composite samples. The complex conductivity of pure ZnO NPs was extracted by applying Bruggeman effective medium
theory. We find that the real part of the complex conductivities increase with the increasing diameter of the ZnO NPs and
are governed by a restricted mean free path for NPs. The results demonstrate that carriers become localized with a
backscattering behavior in nano-structured ZnO.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950Q (2011) https://doi.org/10.1117/12.900486
With the development of terahertz related technologies, the terahertz imaging technology will show its greater practical
value in more areas. In this paper, we describe a terahertz imaging system that uses a single pixel detector in combination
with a series of random masks to enable high-speed image acquisition. The image formation is based on the theory of
compressed sensing (CS). When the scene under view is compressible by an algorithm like JPEG or JPEG2000, the CS
theory enables us to stably reconstruct an image of the scene from fewer measurements than the number of reconstructed
pixels. In this manner, we achieve sub-Nyquist image acquisition. CS theory mainly includes signal sparse representation,
encoding measurement and reconstruction algorithm. CS combines sampling and compression into a single non-adaptive
linear measurement process. Rather than measuring pixel samples of the scene under view, we measure inner products
between the scene and a set of test functions. CS permits the reconstruction of a N-by-N pixel image using much fewer
than N2 measurements. This approach eliminates the need for raster scanning of the object or the terahertz beam, while
maintaining the high sensitivity of a single-element detector. We demonstrate the concept using a backward wave
oscillator (BWO) which is a continuous-wave terahertz source and get a preliminary test result.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950R (2011) https://doi.org/10.1117/12.900492
The transmission spectra of sub-wavelength cross metallic fractal slits in terahertz (THz) frequency region are
presented by means of finite-difference-time-domain (FDTD) simulation. The transmission spectra with multiple pass
bands and stop bands are observed. To understand the physical mechanism of the enhanced transmissions, we simulated
the electric field distribution of THz radiation within the metallic slits at the resonance frequencies by the
electromagnetic design software named CONCERTO. Further analysis reveals that the two transmission peaks in the low
frequency is the local resonance of electric field of the two cross slit, respectively. The third transmission peak is the
co-effect of the two level cross slits. Our simulation is helpful for the understanding of THz wave propagation and THz
transmission through the cross metallic fractal structures. It is also useful for the development of THz photonic devices.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950S (2011) https://doi.org/10.1117/12.900505
Femtosecond pump-terahertz probe studies of carrier dynamics in semi-insulating GaAs have been investigated in
detail under various pump powers. The pump-induced attenuation of terahertz transmission and the carrier relaxation
time are found to be correlated with photo-injected carrier density. These effects can be fully explained in terms of the
enhanced photoconductivity and surface states filling in GaAs. Moreover, abnormal reversal and increase of terahertz
reflected waves transmitted from GaAs are observed, and these phenomena arise primarily from the pump injected
carriers. One-dimensional pump scans of terahertz transmission of both the main peaks and the reflection peaks are
discussed to reveal the more complete studies of the dynamics of carrier transfer in GaAs.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
F. H. Su, G. Sharma, F. Blanchard, L. Razzari, A. Ayesheshim, R. Morandotti, T. Ozaki, F. A. Hegmann
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950T (2011) https://doi.org/10.1117/12.900526
The transient absorption bleaching and velocity overshoot of photoexcited carriers in GaAs and Si have been observed
by the intense few-circle terahertz (THz) probe pulse in the optical pump-terahertz probe (OPTP) configuration. The
free-carrier THz nonlinearity is attributed to the transient electron redistribution in conduction band induced by the
strong THz electric field component.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950U (2011) https://doi.org/10.1117/12.900527
Resonance and absorption peak of transmission spectrum can be achieved when terahertz pulses transmit
through the split-ring resonators (SRRs). Using the theory of LC oscillating circuit and the model of half wave
resonance, we can account for the phenomenon. We once fabricate metal subwavelength dual-ring structure
which is different from the SRRs and there aren't splits in. The resonance and absorption peak, however, still
appear in the THz frequency range. In this time, we respectively fabricate the dual-ring structure and reverse
dual-ring structure on quartz crystal substrate and silicon. When the metal structure is fabricated on quartz
crystal, Using terahertz time-domain spectroscopy (TDS), we find the characteristic spectra exist as well as time
domain waveform and frequency domain spectra of transmitted terahertz pulses present obviously periodic
variation with rotating the sample round the normal of its surface. However, if silicon is used as substrate, the
phenomena will not appear. In this article, we will analyze the phenomena and obtain the reason resulting in it.
We hold that the metal dual-ring structure in itself can't lead to the variation of the terahertz pulses by changing
the sample's angle due to isotropy of the dual-ring structure in surface of the sample. We think the phenomenon
may originate from quartz crystal substrate.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Jessienta Anthony, Rainer Leonhardt, Alexander Argyros, Sergio Leon-Saval
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950V (2011) https://doi.org/10.1117/12.900529
We report measurements for hollow core kagome microstructured Terahertz (THz) fiber characterized with the THz-time
domain spectroscopy (THz-TDS). To achieve good mode overlap between the input beam and the fiber mode
distribution, we incorporate specially designed THz lenses in our experimental setup. The experimental observations
show that only the fundamental mode is guided in the fiber core. The time domain scans and their spectral information
show air-guidance over a large frequency range from 0.6 to at least 1.1 THz. Within this frequency bandwidth, low
transmission amplitudes at certain frequencies are identified as the frequency cut-offs for the kagome structure is
observed. The measured transmission of the kagome fibers shows the characteristics of the inhibited coupling
mechanism. We estimate high coupling efficiencies, as high as 60%, have been achieved in our experiments.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950W (2011) https://doi.org/10.1117/12.900581
In this paper, ZnGeP2 (ZGP) crystal was pumped by a dual-band tunable CO2 laser. Based on the theory of nonlinear
optical (NLO) frequency effect, a new THz light was generated. Under the conditions of three-frequency collinear
nonlinear interaction and type-II phase matching (o+e→o), formulas of phase-matching angle, efficient nonlinear
coefficient, the wave vector direction (θ, Φ), walk-off angle and acceptance angle were derived and relevant curves were
analyzed with software. In this paper, the schematic diagram of THz generation based on ring cavity optical parametric
oscillator (OPO) was designed. Theory analysis showed that the new ring cavity OPO was reasonable and efficient.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Jianjun Liu, Wuxi Ma, Xiuhua Fu, Mengen Zhang, Zhi Hong
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950X (2011) https://doi.org/10.1117/12.900587
The precision of the conventional terahertz transmission measurement system with a parallel-plate sample will be
reduced due to the interference effect, when the frequency of the THz source drifts. In order to solve such problem, a
frequency-drift insensitive transmission measurement system composed of double-path is proposed in this paper, and an
F-P interference model is built. The parameters are optimized, and the effects of the terahertz source's frequency drift on
the precision of both the single- and double- path transmission measurement are analyzed and compared. The results
demonstrated that such kind of measurement system could avoid the influence of the frequency-drift of the THz source,
thus enhance the measurement accuracy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Zi Yu Chen, Hong Su, Chun-Dong Wang, Qiong-Zhou Chen, Shuang-Chen Ruan
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950Y (2011) https://doi.org/10.1117/12.900610
Terahertz (THz) has received significant attentions in recent years, as it promises tempting perspectives in multiple
applications, such as sensing, imaging and spectroscopy, etc. However, most THz systems rely on free space propagation,
where THz wave would experience significant loss. Moreover, most materials have high absorption loss in this spectral
region. A new type of low loss THz waveguides is needed in order to promote the application of THz technologies. In
this paper, we exploit a Teflon solid-core photonic crystal fiber (PCF) and its transmission characteristics have been
numerically investigated in the THz band by using finite element method. Results show that in a large pitch length
(E=2.0mm) dispersion could be as low as 0.01 ps/ (THz·cm) in the range of 1.0 to 2.5 THz. When d/E is larger than 0.45
and E larger than 1.0mm, the modal loss is as low as 0.25 cm-1. It can also be seen that confinement loss can be
eliminated by proper design. The results can provide theoretical references for further studies in this area.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81950Z (2011) https://doi.org/10.1117/12.900667
In this paper, we have determined water-ethanol mixtures and Chinese spirit with terahertz time-domain transmission
spectroscopy (THz-TDS). Eleven samples of water-ethanol mixtures with varying alcohol degree from 0% to 100% (v/v),
increased in 10%-steps, were used as the calibration set. Several Chinese spirit samples were used as the prediction set.
We measured alcohol degree by alcohol meter, with measurement accuracy of 0.2% (v/v). Partial least square (PLS)
model was employed for regression. The refractive index, absorption coefficient and mixed models by PLS regression
together with alcohol degree were established, respectively. The predictive values of alcohol degree were very close to
the reference values determined by alcohol meter. To assess the quality of the model, we calculated the correlation
coefficient R-square, the root mean square errors of the calibration set (RMSEC) and the prediction set (RMSEP) of the
three models. The results show that the absorption coefficient PLS regression model is the best method for determining
alcohol degree of Chinese spirit with THz-TDS transmission measurement.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819510 (2011) https://doi.org/10.1117/12.900671
Soluble solids content is an important index for fruit quality. One of the traditional methods in determining soluble solids
content of fruits is refractometry which measures the refractive index in visible or near infrared. Here we reported the use
of terahertz time-domain transmission spectroscopy (THz-TDTS) technique for the determination of soluble solids
content in apple products. Not only the refractive index, but also the absorption coefficient is used in regression model.
In method one, sucrose solutions were for the calibration set , root mean square of validation set (RMSEP) was 0.168%
for absorption coefficient model, 0.741% for refractive index model. In method two, apple products were for the
calibration set, RMSEP was 0.143% for absorption coefficient model, 0.648% for refractive index model. Less absolute
error of 0.2% between predicted and refractometer value has been both obtained from two methods with absorption
coefficient model. This result proved the THz-TDS technique is quite potential for nondestructive detection on food
quality.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Guo-teng Duan, Bo Su, Ya-qin Zhao, Xiao-yan Wang, Hui-juan Sun, Cun-lin Zhang, Wei-rui Zhao
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819511 (2011) https://doi.org/10.1117/12.900704
Terahertz (THz) technology has huge potential in detection of concealed objects as well as in medical imaging for
non-invasive diagnostics. Recently thanks to improvement of THz sources and detectors, the THz imaging technology
has become the hotspot. This paper presents a real-time imaging system for THz radiation from BWO source. The key
component of the system is the IR-FPA which is a bi-material MEMS detector array optimized for infrared wave lengths.
In order to get a better THz image, the paper presents a modified FPA for THz region. Two main methods were explored
to improve the detector performance in the THz region. The first way identified was the use of novel optical readout
system based on SPR. The second detector improvement approach involved the change of the micro-cantilever structure
that the cantilever of each pixel can shift in vertical direction. A model of one pixel was set up to optimize the structure.
Computer simulations results show that both approaches are effective. The manufacturing of the proposed detector are
also discussed. The technological investigation shows that it is feasible to employ sacrificial layer technique related to
MEMS (Micro-Electro-Mechanical Systems) technology.l.+
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819512 (2011) https://doi.org/10.1117/12.900723
Terahertz radiation, with wavelengths from 30 to 3000 microns, has big potential for
applications such as biomedical sensing, noninvasive imaging and spectroscopy. Current researches
on photonic crystal fibers as THz waveguide has been widely presented, but the sorts of waveguide
usually need special fabrication technique and always be difficult to get perfect structure. We report
on a new type of polymer photonic crystal fibers for low-loss guidance of THz radiation with general
fabrication technique. The use of the cyclic olefin copolymer (COC) Topas, results in THz fibers with
relatively low loss and low material dispersion in the THz range. We manufactured a class of THz
waveguides with different structures. Then we use a THz time-domain spectroscopy system (THz-
TDS) to characterize the Material loss and index of refractive of the waveguides.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819513 (2011) https://doi.org/10.1117/12.900744
We developed a narrow line width terahertz and mid-infrared source based on difference frequency generation(DFG) in
GaSe crystal. The source could be easily continuous-tuned in a terahertz region of 68.1-1386 μm (0.22-4.4 THz) and a
mid-infrared region of 16.1-26.5 m without altering any component. The maximal peak power of terahertz waves is 9.1
W at 143 μm (2.1 THz), which corresponds to a power conversion efficiency of 2.8~10-5. Using a FTIR spectrometer, we
verified the wavelength and the line width of the source.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819514 (2011) https://doi.org/10.1117/12.900765
We present an experimental terahertz (THz) spectroscopic investigation of amino acid using an air-breakdown-coherent
detection (ABCD) system. The strong and ultra-broadband (0.1 to 10THz) terahertz radiations generated by two-color
laser induced air plasma and measured by coherent heterodyne detection. The broadband THz reflection spectra of
L-Lysine (C6H14N2O2) and L-Arginine (C6H14N2O2) are obtained. To solve the phase-retrieval problem in RTDS, the
absorption signatures of the materials are extracted directly from the first derivative of the relative reflectance with
respect to frequency. The absorption features of the two amino acids are characterized in the 0.5~6 THz region. It is
found that both the two amino acids have an absorption peak at 1.10 THz.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819515 (2011) https://doi.org/10.1117/12.900775
Terahertz (THz) radiation has been widely applied in the areas of spectroscopy, sensing and imaging. With the
advancement of THz technologies, THz imaging has been progressed significantly and has huge potential applications in
medical diagnosis, environmental control, chemical and biological identification. In the past, people mainly focused on
overcoming the obstacles in the hardware, such as the limitation of resolution, accuracy and speed in THz imaging
system. In this paper, image enhancement techniques are employed to enhance the contrast and get the better profile of
THz image. Our results clearly demonstrate that digital image processing techniques can suppress noise effectively,
extract target edges robustly, and therefore improve the quality of THz image.181
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819516 (2011) https://doi.org/10.1117/12.900785
The challenges of terahertz (THz) technology exist in the development of new or improved sources of THz
radiation and detection technologies. In general, inexpensive, fast, and room temperature operation THz detectors are not
readily available. A glow discharge neon lamp can serve as a THz detector, and holds great potential for various THz
sensing and imaging applications. Neon lamps THz detector has many advantages such as low cost, fast response time,
large dynamic range, broad spectral range, and room temperature operation. In this paper, the performance of the THz
detector based on glow discharge neon lamps was evaluated. The detector was successfully used in a THz imaging
system, the THz images obtained by the detector was demonstrated and compared with that obtained by a Schottky
detector.at
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819517 (2011) https://doi.org/10.1117/12.900786
Terahertz time domain spectroscopy (THz-TDS) is used to the pure active ingredient of three
benzodiazepine sedative hypnotics with similar molecular structure. The absorption spectra of them
are studied in the range of 0.2~2.6THz. Based on the experiment, the theoretical simulation results of
diazepam, nitrazepam and clonazepam are got by the Gaussian03 package of DFT/B3LYP/6-31G*
method in single-molecule models. The experimental results show that even if the molecular
structure and medicine property of them are similar, the accurate identification of them can still be
done with their characteristic absorption spectra. Theoretical simulation results are well consistent
with the experimental results. It demonstrates that absorption peaks of them in THz range mainly
come from intra-molecular forces and are less affected by the intermolecular interaction and crystal
effects.ô
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Xiao-min Liu, Bei Wang, Xu Lu, Er-jun Liang, Guo-guang Yang
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819518 (2011) https://doi.org/10.1117/12.900788
This paper describes a new concept related to the MEMS(Micro Electro Mechanical system) imaging-array sensors with
the structure of micro-cantilever-arrays for detecting far IR and THz radiation. The measure principle is based on an
improved optical lever and the core component is a set of micro-displacement measuring device with nano-degree
displacement measurement. The amplification coefficient of this improved optical cantilever can reach 102~103 times,
combined with a high resolving power to 10-10m. Compared with focal plane arrays sensors, these tape sensors have the
ability to measure deformations of micro-cantilever-arrays caused by far IR or THz radiation directly, which can
increase the radiation detector sensitivity. The validity of this method is proved by practical experiments. Imaging-array
sensors, based on this measure principle, can be made into a new-type MEMS Far IR or THz sensors.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 819519 (2011) https://doi.org/10.1117/12.900793
In this paper, ZnGeP2 (ZGP) crystal was pumped by a dual-band tunable CO2 laser. Based on the theory of nonlinear
optical (NLO) frequency effect, a new THz light was generated. Under the conditions of three-frequency collinear
nonlinear interaction and type-II phase matching (o+e→o), formulas of phase-matching angle, efficient nonlinear
coefficient, the wave vector direction (θ, φ), walk-off angle and acceptance angle were derived and relevant curves were
analyzed with software. In this paper, the schematic diagram of THz generation based on ring cavity optical parametric
oscillator (OPO) was designed. Theory analysis showed that the new ring cavity OPO was reasonable and efficient.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951A (2011) https://doi.org/10.1117/12.900796
We present a method to extract the polarization of terahertz wave by placing a 4-mm-thick quartz
crystal on the terahertz beam. The polarization and electric field amplitude are varied by a terahertz
polarizer. The quartz crystal is fixed at 45 degree with respect to the horizontal direction and the
terahertz polarization angle can be extracted by the ratio of the two electric field amplitude
corresponding to the ordinary and extraordinary waves that transmitted through the quartz crystal. The
result shows this method is valid to measure polarization of terahertz wave, and it is more convenient
and saving time for only once measure.A
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Jiaqiang Zhong, Sheng-cai Shi, François Pajot, Youssef Atik, Benoît Belier, Frédérique Gadot, Stefanos Marnieros, Michel Piat
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951B (2011) https://doi.org/10.1117/12.900818
We present a new design of an antenna-coupled superconducting transition-edge sensor (TES) bolometer. The incident
radiation is coupled to a membrane-based twin-slot antenna and then transmitted through lossless microstrip lines to
lossy meander-like microstrip lines in which a NbSi film is located between strip and dielectric layer. The NbSi film
serves as both power absorber and temperature sensor (thermometer). With the help of the electromagnetic simulation
software High Frequency Structure Simulator (HFSS), we have studied the performance of the twin-slot antenna. The
simulation results for radiation pattern and return loss show promising prospects for this TES bolometer design. The
power absorption in NbSi film is another important aspect which will be modeled in the future.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951C (2011) https://doi.org/10.1117/12.900825
In this paper, the terahertz time domain spectroscopy (THz-TDS) technology is used to study the
terahertz (THz) spectral characteristics of the Yungang Grottoes weathered material samples
winch collected from No. 4, 9 and 39 these three different caves dug in different periods, A.D.520,
A.D.494 and A.D. 484 years. The available effective wave band is between 0.2-2.6 THz. It is
found that the transmission coefficient is high in low frequency region but low in high frequency
region for all of the three kinds of samples. Experimental results also indicate that all of the
samples have weak absorption in low frequency region, but the absorption coefficient increase
quickly by exponential function as the frequency increasing. This character is more
obvious especially for the absorption spectrum of the samples from the cave of late period. The
refraction coefficient for the three kinds of samples has obvious differences in the whole THz
wave band. The mean refraction coefficient of them is 1.53, 1.57 and 1.51 separately. According
the results above, different periods of caves weathered samples can be identified. In addition, we
can also offer the various optic constant of Yungang Grottoes samples in THz wave band for other
studies work.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951D (2011) https://doi.org/10.1117/12.900827
The amplitude modulation/direct detection (IM/DD) method is adopted to achieve communication in the practical
optical fiber communication system at present. By comparison with the traditional direct detection system, coherent
optical transmission system has a lot of advantages, such as high sensitivity, long relay distance, good selectivity, large
communication capacity and a variety of modulations.
Based on coherent detection principle, ASK heterodyne asynchronous demodulation system is researched and
designed. The signal light and the local oscillator light are mixed through the mixer. Then through the photoelectric
conversion the intermediate frequency (IF) current signal is obtained when the difference frequency signal is input to
detector. And then the signal in form of baseband signal is output after photocurrent signals passing through the electrical
signal processing system. In paper, the circuit of receiver is implemented. And the correctness of circuit design is
demonstrated by experiment. It lays a solid groundwork for further study of Heterodyne Asynchronous Demodulation
System of coherent optical communications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Jia-chun Wang, Yu-min Lu, Min Shi, Da-peng Zhao, Bo Xu, Zong-sheng Chen
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951E (2011) https://doi.org/10.1117/12.900829
There is a close correlation between dielectric loss and complex dielectric constant of non-magnetism
medium, and the former is the macroscopical representation for the later. Relaxation is one of important cause
of the dielectric loss. This paper educes the complex dielectric constant and complex refractive index of
non-magnetism medium in Terahertz spectrum on the base of initial Drude Model, analyzing their
characteristics; it also calculates the Argand Picture of Drude Model, comparing with the counterpoint of Debye
Model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951F (2011) https://doi.org/10.1117/12.900838
Leaf water content is one of the most important indicators of the plant growth status. Thus, for a long-term
research of the plants, the nondestructive and contactless measurement methods are preferable. Recently,
the terahertz (THz) frequency region from 0.1THz to 10THz (or 3-333cm-1) has seen a flurry of research
activity in the fields of physics, chemistry and biology. Terahertz wave is very sensitive to water. This
characteristic suggests the capability of THz spectroscopy for monitoring the water content of the plants. In
this paper, the influence of varying water content in different zones of the same plant on the absorption and
refraction coefficients was given. The influence of varying water content in the different locations of the
mesophyll and mid-vein on the absorption and refraction coefficient was described. And the variations mainly
result from the different thicknesses of leaf. The absorption and refraction coefficients with different relative
water content in the green and yellow leaves were given. These comparisons between green leaf and yellow
leaf reveal that the complex permittivity of leaf is as a complex function of the water content of the leaf. So our
measurements tend to demonstrate that the dielectric material parameters will be employed to determine the
leaf water status in plant leaves. All measurements are in the range of 0.2 to 2.6 THz. These researches will
contribute to the future work of a compact and contact-free THz spectrometer to avoid any damage of the leaf
surface.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Norbert Palka, Danuta Miedzinska, Hubert Oblocki, Robert Panowicz
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951G (2011) https://doi.org/10.1117/12.900860
We report on analysis of epoxy composite reinforced with a glass fiber mat by means of Time Domain Spectroscopy
(TDS) technique in reflection way. The samples consisted of 2 or 3 layers with the beveling angle of the layers equal to
90° and thickness up to 2 mm. Two samples with artificially induced air-bubbles (~1-2 mm in diameter) and a sample
which consisted of the 2 layers of epoxy and a layer of an air-bubble foil between them were also investigated. The
measurements shown that all layers as well as defects can be identified.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Wei Xiong, Wen-feng Sun, Xin-ke Wang, Xue Wu, Yan Zhang
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951H (2011) https://doi.org/10.1117/12.900926
We study a coaxial terahertz waveguide with low transmission loss and broad bandwidth. The coaxial transmission line is
composed of an aurum line in the center, which ento-ectad covered with Teflon layer, wire-mesh, and the dielectric layer
for protection. In this paper, we utilize the finite element method (FEM) to numerically analyze the transmission mode,
the attenuation constant, and the bandwidth of the waveguide. The major transmission properties of the coaxial terahertz
waveguide are calculated for different diameters of aurum axes and different thicknesses of dielectric layers. We also
compare two waveguides with different Teflon thicknesses for getting broader transmission bandwidth. The simulation
results indicate that the optimum dimension of coaxial terahertz waveguide is the aurum axes of 700μm diameter, the
Teflon of 900μm thickness. With these parameters, the average attenuation constant of the waveguide can be as low as
2.44 x 10-4 dB/m in the frequency range 1.0-2.2THz. As these excellent transmission properties and simple structure of
the coaxial waveguide, it can be expected that it will be widely used in terahertz wave communications and the
fabrication of terahertz system integration.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Hong Su, Qiong-Zhou Chen, Hua-Wei Liang, Chun-dong Wang, Shuang-Chen Ruan
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951I (2011) https://doi.org/10.1117/12.900954
In this paper, complex Morlet wavelet transform is introduced to analyze the mode character and the group velocity
dispersion of the metallic cylindrical waveguide in the THz time-domain spectroscopy system. The result shows that the
dominant mode TE11 is separated from the higher mode, and its intension is above 90% of the total. This analysis method
is universal for any THz time-domain spectroscopy system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Ri-ma Bao, Lu Tian, Kun Zhao, Shou-ming Zhu, Li-ming Liu, Guo-zhong Zhao
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951J (2011) https://doi.org/10.1117/12.900988
In this paper, the optical characteristics of crude oil samples from selected territories in Tuha oil field have been
investigated with THz-TDS at room temperature in nitrogen environment. The absorption coefficient and refraction index of
crude oil are calculated in the frequency range of 0.20~2.5 THz. No distinct absorption peak has been found in the spectra,
which may result from the complexity of the constitution of the samples and the water content. The absorption coefficients
increase with the content of wax in the samples with different slopes, which means the intensity of absorption in THz wave
band increases with enhanced density of the sample and unaltered thickness. The average refractive indices were 0.62070,
0.59767 and 0.59290 corresponding to TuLuFan, ShanShan and WenMi territories, respectively. The refractive values show
the phenomenon of abnormal dispersion, which meant the samples had the characters of strong selective absorption in this
wave band. In contrast, we have also utilized Fourier transform infrared spectroscopy (FTIR) in the 400-4000cm-1 to measure
the mid-IR absorption spectra, and the results revealed that the crude oil is more active in the range of Terahertz than in the
mid-IR band. The experiments demonstrated that THz-TDS is a powerful tool to complement the conventional analytical
approaches and can be applied to detect and analyze the features of the constituent in crude oil.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951K (2011) https://doi.org/10.1117/12.900992
We have developed a novel THz detector which uses the cantilever technology and surface plasmon resonance (SPR)
technology to achieve a high sensitivity. The Micro Electro Mechanical System (MEMS) technology is adopted to
fabricate the detector, which comprise thermo-sensitive bi-material micro-cantilever, prism and optical readout system.
The bi-material of Si3N4 and Al is used to fabricate the micro-cantilever because of the good absorption characteristic for
THz of Si3N4 and the great difference in thermal expansion coefficient of the bi-material for the deformation of the
micro-cantilever. In order to increase the deformation of micro-cantilever, the method of computer simulation is used to
obtain the optimal structure of micro-cantilever and the thickness of Si3N4 and Al. The function of the glass prism is to
make the incident light generate total reflection under certain conditions. The gold film is sputtering on the top of glass
slide using the method of magnetron sputtering and it is necessary for the generation of SPR performance. The optical
readout system can make the change of cantilever bending convert to the change of reflection luminous intensity
proportionally. The heat on the micro-cantilever coming from the THz radiation can lose easily in the air, so the detector
is placed vertically in a cylindrical vacuum chamber which is sealed with quartz glasses and polyethylene lamina at the
two end surfaces respectively. The quartz glass is used for the incidence of visible polarized light and the polyethylene
lamina for the THz radiation. In order to maintain the vacuum performance of the chamber, the mechanical pump and
molecular pump are adopted. In static mode, THz radiation absorption raises the temperature of micro-cantilever, so it
bends proportionally. The micro-cantilever bending changes the thicknesses of the gap between the micro-cantilever and
the metallic thin film on the micro-prism. It will result in a shift of the SPR angle. Therefore, the surface plasmon
excitation efficiency and therewith the measured at a fixed incident angle reflectance of a metallic film will be changed
almost proportionally to the cantilever bending. Consequently, the radiation energy of THz can be determined via the
metallic film reflectivity change. Finally, the technology of image processing is introduced in detail.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Stefan Katletz, Nico Vieweg, Benedikt Scherger, Bernd Heinen, Martin Koch, Karin Wiesauer
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951L (2011) https://doi.org/10.1117/12.900994
An enhanced measurement system for terahertz pulsed imaging is presented that is capable of effectively performing
en-face and three-dimensional scans of planar and curved surfaces. The bending of the scanning surface
in one direction is compensated by synchronously advancing the mechanical delay time with the deflection of a
scanning mirror. The second scanning mirror for the fast scanning direction forms a telecentric system and does
not exhibit phase distortion.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951M (2011) https://doi.org/10.1117/12.901048
THz spectroscopy has recently been used to examine human disease because of its a higher sensitivity and
signal-to-noise ratio. In this work, the interaction mode between THZ radiation and biological tissue in the THz
frequency range is given. Clinical Intralipid-10% is diluted into different concentrations to use as tissue phantoms. And
they are firstly tested based on the terahertz time domain spectroscopy in the condition of room temperature. Optical
parameters of phantom solution including absorption coefficient and refractive index are gotten, and the frequency
properties of these optical parameters are analyzed. The function relations can be firstly found. The conclusions is
meaningful to make the further research of interaction between THZ radiation and human tissue, related cancers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951N (2011) https://doi.org/10.1117/12.901054
This paper illustrates the fundamental transmission characteristics of periodic air hole metal array utilizing FDTD
simulations. A metal-dielectric structure with periodic hole arrays perforated in the metal layer is presented. By changing
the values of parameters, such as dielectric constant, thickness of the metal film and hole periodicity, the transmission
responses are explored at terahertz regime. The surface plasmon polaritons play a significant role in the transmission.
Based on the analysis, a wide band-pass filter containing metal-dielectric-metal layers is designed with square lattices of
air holes in metal layers. The parameters of the structures are carefully selected to give a filtering characteristic with
relatively wide and flat pass-band exceeding 200 GHz, over 95% THz transmittance and easy manufacture process. This
kind of sample structure can be the potential candidate of filters in terahertz systems.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Xiao-bo Wang, Juan Chen, Jing Liu, Jian-wei Liu, Hong Ding, Ken-Tye Yong, Ling Ye, Shu-li He
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951O (2011) https://doi.org/10.1117/12.901087
This paper reports a hot colloidal synthesis method toward the synthesis of CuInS2/ZnS hybrid nanoparticles. First,
CuInS2 quantum dots (QDs) were synthesized in the noncoordinating solvent octadecene using copper nitrate, indium
acetate, myristic acid, oleylamine and dodecanethiol. CuInS2 QDs with diameter of 2~10 nm were obtained by tuning the
reaction temperature and time. Secondly, CuInS2/ZnS core/shell QDs with different thickness of ZnS shell were
synthesized by seed-mediated growth method, which can prevent the CuInS2 QDs oxidized and improve their photo
luminance. Low-toxic cadmium-free CuInS2/ZnS QDs with high PL efficiency are expected to be used for bio-label.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951P (2011) https://doi.org/10.1117/12.901094
Terahertz spectroscopy contains rich physical, chemical, and structural information of the materials, and one unique
attribute of terahertz is their ability to sensitively measure the induced molecular dipole moments of many liquid crystals.
In this paper, the transmission spectra of several liquid crystals 5CB, TEB300, LC203000 LCs were measured by THz
time-domain spectroscopy technique and free-space electro-optic sampling method. The refractive indexes of the
mentioned liquid crystals in the THz range are calculated. Furthermore, the optical constants are compared and analyzed,
expecting to fill the spectrum gap of liquid crystals in the THz range and provide the experimental and theoretical
foundation for the application of liquid crystals.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951Q (2011) https://doi.org/10.1117/12.901519
In this paper, a compact terahertz stop band filter is presented, which consists of two parallel metallic surfaces corrugated
with rectangular groove arrays of period a. When a metallic surface is periodically corrugated, surface electromagnetic
modes can be excited by incident terahertz waves. These modes are surface plasmon polaritons with an effective plasma
frequency controlled entirely by the surface geometry. Because of the corrugated grooves and geometry induced highly
confined surface plasmon polaritons, the fundamental mode of the parallel metallic plates splits into two modes and there
is a band gap between the two modes. The band stop filtering functionality is realized by rejecting all frequencies in the
gap. Simulation results calculated by finite element method show that the proposed structure has a band gap ranging
from 0.315c/a to 0.350c/a for groove depth d = 0.5a, groove width l = 0.5a and gap width of the two parallel metallic
surfaces w = 2a. Transmission spectra also show zero transmission within the band gap region where no guided modes
are supported. By varying the gap width w and groove depth d, different filtering bandwidths with different center
frequencies can be achieved.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951R (2011) https://doi.org/10.1117/12.901585
Half-Wave Loss (HWL) plays an important role in the optical effects and devices based on the thin film interference
coatings, such as in fiber optical telecommunication, electron displays, optical storage as well as polarizing beam splitter
with very high extinction ratios in both reflection and transmission. Using the reflective terahertz time-domain
spectroscopy (THz-TDS), we present a direct and unambiguous observation of the polarity reversal due to the half-wave
loss by comparing the single-cycle THz pulse normally reflected from the quartz-air interface with that from the quartzwater
interface. In addition, a quantitative measurement of the phase shift is provided and the impact of the imaginary
part of the complex refraction index on the phase shift is discussed. The measured results are in excellent agreement with
the theoretical predictions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951S (2011) https://doi.org/10.1117/12.901629
A terahertz (THz) imaging system based on air ionizing in two color laser fields is demonstrated. A 1mm thick
(110)-oriented ZnTe is used for electro-optic sampling crystal. The depth of modulation of THz is 0.8%, which is much
lager than that of optical rectification in ZnTe. Minus the background, the transmission images of the THz focus and a
moving metal rod are demonstrated. The imaging speed is 34 fps. It is very useful to observe the movement of objects
with terahertz in real time.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Jing Guo Huang, Bing Bing Wang, Jin Xing Lu, Zhi Ming Huang
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951U (2011) https://doi.org/10.1117/12.902301
The terahertz radiation from the crystal of Cadmium Telluride (CdTe) can be achieved in difference frequency generation
(DFG) experiment of 1064 nm nanosecond laser for collinear configuration. For the isotropic crystal CdTe, the exact
phase matching could not be fulfilled by the two NIR lasers. However, if the interaction length is smaller than the
coherent length, quasi-phase matching could be achieved. In order to understand the property of the coherent length in
CdTe, the property of the refractive index and the absorption coefficient at the THz region is analyzed by two kinds of
transmission spectra: one from Terahertz Time-Domain Spectroscopy (TDS) and the other from Fourier Transform
Infrared Spectrometer (FTIRS). From the transmission spectra of FTIRS, four absorption lines are detected: 2.1 Thz, 4.2
Thz, 7.4 Thz, and 8.6 Thz. Also additional two little absorption peaks occurred at 1.6 Thz and 1.8 Thz. This maybe
explained by the phone mode LO-LA and LA-TA, respectively. Below 1.0 Thz, the absorption coefficient is small and
constant (about 5cm-1). Based on the refractive index spectra of THz-TDS, the coherent length calculated increases
linearly with the THz wavelength in the region of 200μm to 900μm, with its' value 3.6 mm at 300μm. Then
interaction length can be long enough to satisfy the quasi-phase matching condition. A high power and compactable
terahertz source can be obtained from CdTe under 1 Thz, which can be tuned continually and operated under room
temperature.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951V (2011) https://doi.org/10.1117/12.902302
Nowadays, heavy metals pollution is becoming a serious problem in agriculture. This paper reports a
preliminary work on a feasibility study of applying terahertz (THz) technology for heavy metal ions
detection in soil. This study was first conducted at Oklahoma State University, and then carried out at
China Agricultural University and Capital Normal University. Pure soil was collected in an
experimental field, which contains nearly no heavy metal ions from standard detection; in the
experiment, heavy metal ions were mainly Pb2+, Cr3+, Zn2+ and Cu2+ from chemical compounds. Based
on the National Standard for Heavy Metals Pollution, a set of soil samples with different polluted levels
were prepared in the lab. The metal ions concentration levels were selected as 50ppm, 300ppm and
700ppm. Each soil sample was pre-processed by collecting, weighing, mixing, drying, grinding and
labeling before measurements. The thickness of soil samples was selected as 1.5mm and 3mm. The
absorption spectra for the soil samples with different heavy metal ions were collected using THz
time-domain spectroscopy (THz-TDS) equipments separately at Oklahoma State University and
Capital Normal University. The test results showed that soil samples with Pb2+, Cr3+, Zn2+ and Cu2+ had
different absorption characteristics within the bandwidth of 0.1-1.1THz. A narrow bandwidth only up
to 1.1THz was got because the soil particles showed much absorption and scattering properties to the
THz spectroscopy. Different soil samples with different concentration of heavy metal ions also showed
much difference and it could be used to predict the heavy metal concentration in the future. The results
from the preliminary study show a potential of THz technology applied for heavy metal ions detection
in agricultural fields environment. However, since the high scattering features of samples and high cost
of equipments, the measurement methods and practical issues needs to be further investigated and
improved to make the THz technology a feasible tool for soil heavy metal ions detection.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
Vyacheslav A. Trofimov, Svetlana A. Varentsova, Norbert Palka, Mieczyslaw Szustakowski, Tomasz Trzcinski, Sheng Lan, Hai-Ying Liu
Proceedings Volume International Symposium on Photoelectronic Detection and Imaging 2011: Terahertz Wave Technologies and Applications, 81951W (2011) https://doi.org/10.1117/12.903558
The influence of an absolute phase of the THz pulse with a few cycles on the spectrum and spectral dynamics of signal
reflected from or transmitted through the explosive or paper sheet is analyzed for problems of the detection and
identification of explosive. The signal was measured on the long-term interval with duration about 180 ps and contains
both the main reflected THz pulse and the subpulse with less intensity. Two cases of the reflection (normal and specular
reflection) of the THz pulse from the RDX are considered. For the THz pulse interaction with the paper sheet the
transmission mode is analyzed. Dependence of the nonlinear response of substance from the absolute phase of pulse is
illustrated by examples of SHG or self-action of laser pulse with a few cycles. We showed that the absolute phase of
pulse plays one of the key roles for the detection and identification of the substances at the reflection mode. It is
necessary to investigate this problem with big attention during next few years.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.