Previous research demonstrated that two-soliton interactions can lead to nonreciprocal soliton amplification, a mechanism that can accumulate energy for rogue wave formation as soliton interactions increase. The question arises whether three or more soliton collisions can lead to amplification or chaotic behavior, akin to the three-body problem in particle physics. Through experiments and simulations using a photorefractive potassium-lithium-tantalate-niobate (KTN:Li) crystal, our study explores multiple soliton collisions with strong nonreciprocal energy exchange. Chaotic dynamics and intense wave formation are observed after a collinear three-soliton collision. However, when an additional dimension without broken inversion symmetry is introduced, the solitons consistently fuse into an intense wave instead of exhibiting chaos. This insight highlights the role of dimensionality and nonreciprocal energy exchange in determining soliton behavior and rogue wave formation. The study underscores the analogy between solitons and particles, linking chaotic behavior in three-body physics to the emergence of rogue waves.
We present a methodology for quantitative sensing of the contents of a target material (TM) in a given sample which employs biosensing bioluminescent bacteria. These bacteria are genetically engineered to respond to the presence of a specific TM in their microenvironment by producing bioluminescence. Herein, we extend this methodology to include quantitative sensing of the TM content in the inspected sample by exploiting the dependence of the bioluminescence produced by the bacteria on the content of the TM in the inspected sample. However, employing bacteria as precise measurement devices is inherently problematic, as the signal they produce varies between different batches of bacteria, and changes as the batch ages. Moreover, As the methodology is designed for outdoor operation, the sensitivity of the bacteria response to changes in the environmental conditions needs to be taken into account. These hurdles are overcome in a special optoelectronic sensor which measures in parallel the responses produced by the inspected sample, and a standard sample containing a known quantity of the TM. Both measurements are conducted by identical sensing channels using bacteria from the same batch, and under the same environmental conditions. The “standard ratio” (SR) defined as the ratio between the maximum responses of the inspected sample and the standard sample was found to be independent of the batch and environmental conditions. A calibration curve of the SR vs. the TM concentration in a set of preprepared samples is used to gauge SR at the sensor output to the TM concentration in the inspected sample.
The electro-optic performance in free space at the 2 μ𝑚 wavelength range of potassium lithium tantalate niobate (KLTN) crystal operated at the paraelectric phase close to the phase transition temperature (Tc) is explored. An electrically induced change in the refractive index approaching 0.01 was demonstrated close to the phase transition temperature, while maintaining high optical quality and transparency at a wavelength of 1.85 μ𝑚. A special crystal geometry was employed in order to suppress unwanted acousto-optic oscillations that were superimposed on the generated pulse due the strong electrostriction of KLTN close to Tc.
Electro-optic active Q-switching in a Tm:YLF laser operating at 1.88 μm is demonstrated using a potassium lithium tantalate niobate (KLTN) crystal as the electro-optic medium. Upon approaching the ferroelectric phase transition temperature, KLTN manifests an exceptionally strong quadratic electro-optic effect. Operation with low driving voltages of 550V on a 3 mm wide and 2mm long crystal were demonstrated. Pulse energy of 1.4 mJ with 17 ns pulse duration was obtained at 1 kHz repetition rate with 9.5W incident pump power. A special trapezoidal configuration of the KLTN crystal was used in order to suppress the acousto-optic oscillations that are generated due to the strong electrostriction manifested in KLTN close to the phase transition temperature which lead to strong instabilities in the laser performance. New EO Q switching mechanism was implemented, in which the resonator gain rather than the loss was shifted between two levels by exploiting the different gain of the Tm:YLF crystal in the and polarizations. This obviated the need for inserting a polarizer in the laser cavity, and allowed the shortening of the laser cavity.
A method for creating photorefractive electroholographic gratings with sustained operational longevity is presented and demonstrated. The method circumvents the thermal decay and erasure during readout characteristic of photorefractive devices by augmenting the device with a built-in mechanism that writes and periodically and/or continuously refreshes the space-charge gratings which are the core elements of such devices. The mechanism was demonstrated in a slab waveguide constructed in a KLTN:Cu crystal. The space-charge grating was created by illuminating the slab waveguide through a binary grating mask deposited on top of the surface of the crystal by incoherent illumination from a LED. The electroholographic performance manifested by the grating was similar to that of gratings constructed by interfering beams. This makes electroholography to be the basis for a viable technology for performing wavelength selective switching and electrical wavelength tuning at the device level, and enables their assembly in integrated photonic circuits.
We describe a biosensing module in which live bacteria, genetically “tailored” to respond to the presence of a specific target material, constitute the core sensing element, reporting their response by bioluminescence. The module is constructed of two channels: an ‘induced’ channel that measures the bioluminescent light emitted by bacteria exposed to the inspected area, and a ‘reference’ channel that measures in parallel the bioluminescent light emitted spontaneously by bacteria of the same batch. This enables to overcome signal variations generated by different batches of bacteria, and due to varying environmental operating conditions. A special low-noise optoelectronic circuit was constructed to detect the bioluminescence emitted by the bacteria in both channels. The bacteria are encapsulated in polymer beads that also contain nutrients and water, enabling long-term maintenance-free operation. The beads are packaged in special cassettes at the bottom of the module, so that the induced channel cassette is in direct contact with the ground underneath the module, whereas the reference channel cassette is isolated from the ground. The module contains, in addition, a digital signal processing unit, and a wireless communication unit. The module is designed to operate outdoors as an autonomous network element designed for large scale in-situ deployment. The module described herein was developed for the detection of buried landmines, by sensing the presence of 2,4-dinitrotoluene (DNT) vapors released by the mine, accumulating in the ground above it. Detection of DNT in the sub-ppm range is demonstrated.
Current landmine detection methodologies are not much different in principle from those employed 75 years ago, in that they require actual presence in the minefield, with obvious risks to personnel and equipment. Other limitations include an extremely large ratio of false positives, as well as a very limited ability to detect non-metallic landmines. In this lecture a microbial-based solution for the remote detection of buried landmines described. The small size requirements, rapid responses and sensing versatility of bacterial bioreporters allow their integration into diverse types of devices, for laboratory as well as field applications. The relative ease by which molecular sensing and reporting elements can be fused together to generate dose-dependent quantifiable physical (luminescent, fluorescent, colorimetric, electrochemical) responses to pre-determined conditions allows the construction of diverse classes of sensors. Over the last two decades we and others have employed this principle to design and construct microbial bioreporter strains for the sensitive detection of (a) specific chemicals of environmental concern (heavy metals, halogenated organics etc.) or (b) their deleterious biological effects on living systems (such as toxicity or genotoxicity). In many of these cases, additional molecular manipulations beyond the initial sensor-reporter fusion may be highly beneficial for enhancing the performance of the engineered sensor systems. This presentation highlights several of the approaches we have adopted over the years to achieve this aim, while focusing on the application of live cell microbeads for the remote detection of buried landmines and other explosive devices.
Recent studies of the minute morphology of the skin by optical coherence tomography showed that the sweat ducts
in human skin become helically shaped tubes in the Epidermis and are filled with an aqueous solution. When
considered as entities embedded in a dielectric media, they resemble helical antennas. The spectral response
obtained by our computer simulations coincides with the analytical prediction of antenna theory and support this
hypothesis, if a fast enough current mechanism exists in the duct. In particular the strongest spectral response of the
simulation was noted around the predicted frequencies (240 GHz and 380 GHz) for the respective normal and axial
modes of the helical structure. Furthermore, circular dichroism of the reflected electromagnetic field is a
characteristic property of such helical antennas and it was shown that it is indeed a characteristic of the simulation
model. Fast proton hopping is posited as the current mechanism.
Consequently experimental evidence is presented that the spectral response of the skin in the sub-Terahertz region is
governed by the level of activity of the perspiration system. This in turn is moderated by the Sympathetic Nerve
Response and is demonstrated by the correlation to physiological stress as manifested by the pulse rate and the
systolic blood pressure. These physical relaxations are tonic in nature (lasting more than a minute). Could the phasic
characteristic of emotional excitation also be evident in the reflection coefficient? By applying techniques borrowed
from psychiatric science we hope to answer this point in our paper.
In this paper we describe recent progress in the study of scale-free optical propagation in super-cooled nonergodic
ferroelectrics. Our experimental and theoretical findings indicate that a regime can be found in which
diffusion-driven photorefractive effects can fully annul the diffraction of focused laser beams. This demonstrates
that diffraction can be systematically eliminated from an optical system and not simply compensated, with
fundamental implications for optical imaging and microscopy. The effect transfers directly from the paraxial
regime into the non-paraxial regime described by the Helmholtz Equation, and suggests a means to achieve the
propagation of super-resolved optical images. The result is a nonlinear-based metamaterial, even though the
underlying nano-structuring of the ferroelectric is random and the effect is both non-absorptive and wavelengthindependent
for a wide spectrum.
Refractive index engineering (RI_Eng) by ion implantations is a generic methodology for constructing multi-component
integrated circuits of electrooptic and nanophotonic devices with sub-wavelength features operating in the visible - near
IR wavelengths. The essence of the method is to perform spatially selective implantations for sculpting complex 3D pre-designed
amorphized patterns with sub-wavelength features and reduced refractive index within the volume of the
substrate. A number of devices that were constructed in a substrate of potassium lithium tantalate niobate are described,
including a submerged slab waveguide, an optical wire and a channel waveguide array.
We present a new technology for uncooled focal plane arrays, which is based on optical readout. An electrooptic crystal, operated in the paraelectric phase, is used as the temperature sensitive element. A lateral readout configuration is utilized, and an entire row of pixels is read simultaneously through electrical triggering. The optical readout diminishes the electronic noise mechanisms resulting in a predicted NETD of 5-7mk. This low NETD of the device is determined by the temperature fluctuations noise, thus approaching the theoretical limit for uncooled FPAs.
Hologram writing and fixing mechanisms are examined in disordered conjugated polymer/glass composites. The conjugated polymers used were alkoxy substituted poly(phenylenevinylne) analogs and the glass matrices were zirconia-organosilica xerogels. Hologram formation mechanism is shown to be a photochromic process consisting of light induced photo- oxidation (bleaching) of the embedded conjugated polymer resulting in the formation of an absorption grating and a phase grating. IR and Raman spectroscopy show that the chemical transformations upon photo-bleaching involve chain scission and oxidation of the polymer at the vinylic position of the conjugated polymer. Oxygen removal increases hologram formation time by more than an order of magnitude and halves the total hologram efficiency. The oxygen dependence was also highly correlated with photo-bleaching of the samples and beam interaction of the writing beams. Light sensitivity was compared for several polymer/glass composites showing that the new composites and film preparation techniques are promising for blue and ultraviolet sensitive holographic materials. A hologram fixing method based on a PMMA coating, applied on the film after hologram formation is demonstrated and shown to increase hologram erasure times by four. These important findings show that conjugated polymer/glass composites based storage media can be manufactured and fixed efficiently for a long term based on this method.
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.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
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.