This paper provides computed results elucidating the nature of resonant leaky modes associated with periodic refractive-index lattices such as gratings and photonic crystals. Computed Brillouin diagrams illustrate the association of the guided-mode resonance with the second stopband demonstrating the effects of grating profile symmetry and its Fourier harmonic content. Examples of wideband bandpass filters are given and the influence of variations in some of the design parameters on their spectral features is numerically evaluated. Reflectors with wide spectral and angular apertures are presented and their parametric sensitivity explored. Single-layer polarizers are demonstrated. Addition of homogeneous layers to enhance spectral features of the elements is briefly examined.

The number of independent lattice constants of three-dimensional photonic crystals, which can be fabricated by four-beam interference, is analyzed for 14 Braivas lattices. The equation of maximum intensity point condition for interference fringe among four plane waves is the same as that between the lattice vector and the reciprocal lattice vector in the solid-state physics. This relation gives us the way to derive the wave number vectors for incident four plane waves to fabricate any desired three-dimensional photonic crystal structures. It is analyzed that the effective combination of incident wave number vectors is 16 for each of 14 Bravais lattices. Lattice constant is numerically analyzed for 16 combinations of wave number vectors for each 14 Bravais lattices. The resultant 16 lattice constants are not necessarily independent due to the symmetry of lattice. It is found that the maximum and minimum numbers for lattice constants are 16 for Triclinic and Face-centered orthorhombic lattices, and 1 for Primitive orthorhombic, Primitive tetragonal and Primitive cubic lattices. The others are 10 for Centered monoclinic, 9 for Body-centered orthorhombic, 6 for Body-centered tetragonal, 5 for Face-centered cubic, Body-centered cubic and Trigonal, and 2 for Primitive monoclinic, Centered orthorhombic and Hexagonal lattices. As a result, total number of 81 photonic crystals with different lattice structure or different lattice constant can be fabricated by using four-beam interference with a fixed wavelength.

By trapping photons in fabricated phase-shift defects magnetic photonic crystals can enhance the Faraday rotation in magneto-optic films. The integration of these structures into on-chip photonic circuits, while advantageous from the point of view of component connectivity in multi-functional systems, faces several challenges. Differences in effective refractive indices between transverse electric (TE) and transverse magnetic (TM) modes engender phase disparities, thus hindering the Faraday response of the material. Moreover, photonic waveguide structures in magnetic films may support more than one mode depending on the waveguide thickness and refractive index. The effects of birefringence and multimodality on the performance of waveguide magnetic photonic crystals in magnetic garnets are discussed in paper. Particular attention is paid to analyzing the effect of Faraday rotation enhancement in magnetophotonic crystals in the presence of waveguide birefringence and modal multiplicity. Multiple stopbands and significant polarization rotation are observed in multimode Bi-substituted iron garnet film waveguides with single-defect photonic crystal structures. A spectrally flat response is predicted for the polarization rotation in first order mode for birefringent waveguides. The photonic crystals for this study are patterned on ridge waveguide films by focused ion beam (FIB) milling.

Photonic crystal structures are of great practical interest because they allow light to be strongly confined and manipulated at scales on the order of one wavelength. Useful photonic crystal devices have been demonstrated, but these structures can be improved upon by using better simulation tools. Topology optimization is presented here as one approach for designing improved photonic crystal structures. Topology optimization is a numerical technique that uses nonlinear programming techniques and design sensitivity analysis by the finite element method to calculate improved photonic crystal structures. The general technique is outlined, and the case of a waveguide termination in a square lattice rods-in-air photonic crystal is demonstrated. A compact waveguide termination is designed that shows a fivefold increase in power incident upon a target area over a simple termination.

Two-dimensional photonic crystals of titanium dioxide are predicted to have many advantages over semiconductor photonic crystals, e.g., silicon and GaAs: in particular, low optical loss in the near infrared region used for optical communication, low thermal expansion, and a refractive index which is close to that of optical fibers. However, it is difficult to create micro-nano structures in titanium dioxide, since semiconductor micro-fabrication techniques cannot be applied to titanium dioxide. As the first step, we calculated the photonic band gap of titanium dioxide rod-slab on SiO₂. Band gap percent against thickness of the rod-slab was also examined. Finally, we confirmed the most suitable structure for 2D photonic crystals. A deep X-ray lithography technique was employed to create a very deep and precise template. Liquid-phase deposition was then used to faithfully deposit a tightly packed layer of titanium oxide onto the template. Finally, the template was selectively removed to obtain a photonic nano-structure. A template for the most appropriate three dimensional structure was also fabricated using the method proposed by Yablonovitch. By employing the same method, we successfully obtained the 3D structure of TiO₂.

We report on the fabrication and characterization of the first periodic sub-micron scale one- and two-dimensional surface structures in congruent 500 μm thick lithium niobate crystal samples. Structures with periods from 2 μm down to 500 nm, lateral feature sizes down to 200 nm and depths around 10 μm, largely compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by selective wet etching of ferroelectric domain engineered samples obtained by electric field poling performed at an overpoling regime. Holographic lithography is here used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short-pitch fabricated structures are attractive in a wide range of applications, such as nonlinear short-wavelength conversion processes, backward second-harmonic generation, fabrication of novel tunable photonic crystal (PC) devices, electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for PC applications, accurate and complete topographic characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures. Interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.

We demonstrate a promising method to fabricate large-area photonic crystals with desired defects by using the combination of interference and multi-photon polymerization techniques. Multiple-exposure of two-beam interference pattern at 325 nm into a negative SU-8 photopolymerizable photoresist is used to form a square or hexagonal twodimensional periodic structure. Arbitrary defects are introduced in these structures by tightly focused (numerical aperture 0.85) 100 fs duration pulses at 830 nm to generate multi-photon polymerization effect. The experimental evidence of 6 mm × 6 mm photonic crystals with the lattice constant as small as 1 μm embedding several kinds of defect proves the concept and shows this technique potentially useful for photonic researches and applications.

A simple optical interference method for fabricating two- and three-dimensional (2D and 3D) periodical structures is theoretically and experimentally demonstrated. Multiple-exposure of two-beam interference pattern into a photopolymerizable resist creates high quality 2D or 3D microstructures. The type of periodic structure depends on the orientation of the photoresist with respect to the laser beams and the number of exposure. Square or hexagonal structures are obtained by choosing an angle of 90° or 60°, respectively, between two different exposures. 2D structures are obtained with two or three equal exposures. 3D structures with different types (bcc, fcc, Woodpile, etc.) are obtained with three or four exposures and appropriate rotation angles. This method presents many advantages over others using multi-beam (three-, four-, or five-beam) interference: i) easy to fabricate different structures(hexagonal or square) by simply rotating the sample, ii) best contrast between the minimal and maximal intensities of interference pattern due to the identical polarization of two laser beams in the interference area, iii) in particular, 3D periodical structures have the same period in three dimensions, which can't be obtained by one exposure of multi-beam interference. The experimental results obtained with SU-8 negative photoresist are well in agreement with the theoretical predictions. Such fabrication technique can be useful for applications in photonic crystals research.

We propose and report a novel photonic crystal (PhC) encapsulation concept, where the originally exposed air holes are sealed off on top of the surface to create an enclosed air column structure in two dimensional (2D) PhC based devices and systems. The impact of encapsulation on the photonic bandgap will be discussed for different encapsulation conditions. Experimental results on encapsulation process will also be reported, with focus on the nanoparticle based self assembly encapsulation. Finally a novel photonic crystal surface emitting laser based on this encapsulation concept will be proposed and discussed. The surface state induced non-radiative recombination and different electrical injection schemes will be discussion with the benefit of encapsulation being discussed in the end.

The nanoimprint technology is attractive for the fabrication of nano-scale structures in view of cost and mass production. There are several points for the industrial applications such as pattern formation area, resolution, residual layer thickness, precise control of pattern transfer, lifetime of mold, alignment and so on. A thermal nanoimprint system, which can imprint fine dots on a 300 mm diameter wafer in a single step, is developed. The narrow pith patterns for future storage and IT devices are formed on a polymer layer. A high-aspect nanoprint (Hi-NP) technology forms polymer nanopillars with high aspect ratio. The nanopillars are applied to a bio-chip for the fluorescence immunoassay. The chip is effective in the enhancement of the fluorescence intensities, since the nanopillars enlarge the surface area.

Nano-optic retarders and polarizers based on dielectric and metal nano-gratings were fabricated by UV-nanoimprint lithography. Different from conventional nanostructure-based optical devices, atomic layer deposition, a highly uniform and conformal deposition process, were utilized to fill trenches of the both dielectric and metal nano-gratings. The resulted immersion nano-grating design opens a path for innovative nano-grating based optical devices and integrated optical devices. As an example, a high-performance fully-buried aluminum nanowire-gird polarizer was developed which allowed us to achieve a monolithically integrated visible circular polarizer. The ability to integrate multiple nanostructure-based optical layers opens a path for innovative integrated optical devices as well as a new strategy for driving both miniature and cost.

Aluminum nanowire-grid polarizers and polarizing beam splitters with a fixed pitch (i.e., period) of ~146 nm but a wide range of linewidths (from < 60 nm to 90 nm) and heights (from 150 nm to 200 nm) are studied. Immersion interference lithography, UV-nanoimprint lithography and aluminum reactive ion etching were used to fabricate the nanowire-grid polarizers. Optical performance of the nanowire-grid polarizers was characterized in a broad spectral range from UV (< 400 nm) to near infrared (> 1700 nm). The performance trade-off between transmittance/reflectance and extinction ratio is investigated in details. The developed high-performance large-area broadband nanowire-grid polarizer opens the potential for many optical applications particularly integrated optics.

We are studying on photonic DNA computing, in which the nature of light and DNA is effectively utilized, as a new computing technique. In the scheme, computation is performed by manipulating DNA with chemical reactions at nano-scale and control of light at micro-scale. As a fundamental operation, translation of DNA molecules from a position to another one is important. This paper describes some experimental results on translation of DNA molecules. A DNA cluster is fabricated by making hybridization of anti-tag DNA and data DNA that is complementary to the anti-tag DNA. The translation method consists of three steps; (i) attaching data DNA to beads (fabricating DNA clusters), (ii) translation of DNA clusters, and (iii) detaching the data DNA from the beads. We confirmed that VCSEL array optical manipulation is applicable to step (ii). For steps (i) and (iii), hairpin DNA is used to achieve two stable states of DNA. The experimental results demonstrated that attaching data DNA to a bead and detaching the DNA from the bead is possible by laser irradiation with an appropriated irradiation schedule. These results show effectiveness of the optical technique for controlling DNA molecules locally.

We describe nanoengineered polymeric materials, their properties, and their use to produce state-of-the-art integrated optical components with optimal optical, electrical, mechanical, and thermal properties. These components met all performance and reliability requirements in the telecommunication industry, including Telcordia GR-1209/GR-1221 qualification, as well as accelerated aging tests that significantly exceed Telcordia requirements, such as aging at extreme temperature (5000 hours at 175°C) and optical power (6000 hours at 1.5 W of 1550 nm light). The types of components we describe include variable optical attenuator arrays, intelligent optical cross-connects, and fully reconfigurable optical add/drop multiplexers.

We present a novel polymer-chain-controlling and selective growth technique to make high-index-contrast (HIC) waveguides and photonic crystals. In the present work, poly-azomethine (poly-AM) films that are conjugated polymer were grown on substrates with surface treatment by chemical vapor deposition (CVD) using p-phenylenediamine (PPDA) and terephthalaldehyde (TPA) as reactive source monomers. For polymer chain controlling, poly-AM films were grown by CVD on SiO film, which was obliquely evaporated on a substrate tilted along the y-axis. The chains on the SiO film were found to be aligned along the y-axis. For selective growth, on a glass substrate surface, where a hydrophobic treatment was applied using hexamethyl-disilazane (HMDS), a hydrophilic SiO thin film was deposited through a metal mask by the vacuum evaporation to form a hydrophilic/hydrophobic pattern. The poly-AM thin film was found to be selectively grown on the SiO region, that is, on the hydrophilic region, without growth on the hydrophobic region. These results demonstrate a potentiality of the proposed technique to provide a wide range of three-dimensional fine structures.

The results of experiments on micromachining of organic polymers by direct photo-etching using a compact laser plasma soft X-ray source based on a gas puff target are presented. Soft X-ray radiation in the wavelength range from 2 to 15 nm was produced as a result of irradiation of a double-stream gas puff target with 0.8 J/3 ns laser pulses from a Nd:YAG laser. The soft X-ray pulses with energy of about 100-200 mJ in a single pulse were used to irradiate samples from organic polymers to form microstructures. The obtained results show that direct photo-etching using the laser plasma soft X-ray source could be useful for micromachining of organic polymers. Strong enhancement of the photo-etching process was observed for the samples heated up to 140^oC.

We report on the design, fabrication and integration of micro/nano-scale optical waveguide arrays and devices for optical printed circuit board (O-PCB) and VLSI photonic applications. The O-PCBs perform the functions of transporting, switching, routing and distributing optical signals on flat modular boards or chips in a manner similar to the electrical printed circuit boards (E-PCBs). The photonic devices include microlasers, microlenses, micro-reflectors, couplers, arrayed waveguide grating structures, multimode interference (MMI) devices and photodetectors. For VLSI micro/nano-photonics we used photonic crystals and plasmonic metal waveguide structures. We also describe device characterization using near filed scanning microscopy. We examine the scientific and technological issues concerning the miniaturization, interconnection, and integration of photonic devices, circuits and systems in micron or submicron scale. In miniaturization, the issues include size effect, proximity effect, energy confinement effect, microcavitiy effect, single photon effect, optical interference effect, high field effect, nonlinear effect, noise effect, quantum optical effect, and chaotic noise effect. In interconnection, the issues include homogeneous interconnection (between identical devices) and heterogeneous interconnection (non-identical devices). In integration, the issues of interfacing same kind of devices, two different kinds of devices, and several or many different kinds of devices are addressed. The discussion includes the nano-scale electron beam system and techniques to characterize nano-scale structures.

A novel micro-electro-optic filter formed by integrating photonic crystals with photodiodes on a silicon substrate is demonstrated in this paper. P-n diodes were fabricated on a Silicon wafer using standard processes. Reactive ion etching (RIE) was used to form trenches into the diodes to contain and position photonic crystals. The wafer was then immersed vertically into a slowly evaporating colloidal suspension of silica mircrospheres to assemble the photonic crystal over the photodiodes. Spectral measurements using a grating monochrometer confirmed that a dip exists in the photocurrent response of the photonic crystal filter-photodetectors at the predicted wavelength of 600 nm. We performed a series of measurements using several different sphere sizes and light incidence angles to further characterize the filters, and evaluated the use of device as a wavelength selective detector. Since silica has a low coefficient of thermal expansion, the wavelength selective characteristics of the device are expected to be insensitive to ambient temperatures.

In this paper, we present an overview of 3-D image sensing, formation, and visualization using micro-optics structures embedded in integral imaging (II). As 2-D sensors and 2D display panel technologies advance rapidly, real-time 3D sensing and imaging have shown great promise for 3-D sensing, 3D TV and 3D visualization.

A high resolution refractive-index sensor with a guided-mode resonant grating has been proposed. The gratin has a two-dimensionally periodic structured surface, which is covered with liquid to be measured. The resonant wavelength depends on the polarization states of light for oblique incidence. The change in refractive index of the liquid is determined from the difference of reflectance (or transmittance) between the P and S polarized light waves. The lattice structured silica substrate with a period of 380 nm was made. And a hafnium-dioxide thin film was deposited on the substrate. When the grating surface was covered with water, the measured reflectance had resonant peaks at a wavelength of 615 nm for S polarization and 617 nm for P polarization at an incident angle of 0.5°. For a wavelength of 616 nm, the difference of transmittance of P and S polarization was in linear relation to the change in refractive index. The refractive index was detected with a resolution of 4x10^-4 in a measurement range of 0.064.

We present a class of spectrometers that work based on diffractive properties of spherical beam volume holograms. The hologram in these spectrometers is recorded by a plane wave and a spherical beam and acts as a spectral diversity filter (SDF), which maps different input wavelengths into different locations in the output plane. The experimental results demonstrate that the spherical beam volume holograms have the capability of separation different wavelength channels of a collimated incident beam. For the analysis of the spherical beam volume hologram, a new theoretical method is introduced and used. It is shown that the experimental results are in good agreement with the theoretical study. Using these results, we demonstrate a Fourier-transform volume holographic spectrometer formed by a Fourier-transform lens, a spherical beam volume hologram, and a CCD. We show that this spectrometer can operate well under spatially incoherent light illumination without using any spatial filter (i.e., slit) in the input. We finally introduce a new implementation of a spectrometer for diffuse source spectroscopy by using only a volume hologram, recorded by two spherical beams, and a CCD. The proposed spectrometer is very compact, inexpensive, less sensitive to optical alignment, and has potentially high throughput that can be widely used in biological and environmental sensing applications.

Although the Raman effect is nearly two orders of magnitude stronger than the electronic Kerr nonlinearity in silicon, under pulsed operation regime where the pulse width is shorter than the phonon response time, Raman effect is suppressed and Kerr nonlinearity dominates. Continuum generation, made possible by the non-resonant Kerr nonlinearity, offers a technologically and economically appealing path to WDM communication at the inter-chip or intra-chip levels. We have studied this phenomenon experimentally and theoretically. Experimentally, a 2 fold spectral broadening is obtained by launching ~4ps optical pulses with 2.2GW/cm² peak power into a conventional silicon waveguide. Theoretical calculations, that include the effect of two-photon-absorption, free carrier absorption and refractive index change indicate that up to >30 times spectral broadening is achievable in an optimized device. The broadening is due to self phase modulation and saturates due to two photon absorption. Additionally, we find that free carrier dynamics also contributes to the spectral broadening and cause the overall spectrum to be asymmetric with respect to the pump wavelength.

With a reverse biased p-i-n structure embedded in a silicon waveguide, we efficiently reduced the nonlinear loss due to two photon absorption induced free carrier absorption and achieved continuous-wave net gain and lasing in a silicon waveguide cavity on a single chip. We report here the laser characterization for different cavity lengths from 1.6 to 8 cm. With a pump wavelength at 1550 nm, the laser output at 1686 nm is single mode with over 55 dB side mode suppression and has less than 80 MHz linewidth. The lasing threshold depends on the p-i-n reverse bias voltage. With 25V bias, the threshold pump power is ~180 mW. The slope efficiency is ~4.3% for a single side output and a total output power of >10 mW can be reached at a pump power of 500 mW. The laser wavelength can be tuned by adjusting the wavelength of the pump laser. In addition to the laser line at Stokes wavelength, a narrow linewidth anti-Stokes line at 1434.3 nm is also generated in the laser cavity through parametric conversion process.

Two-photon photopolymerization has been recently considered one of the most important micro-nanofabrication technologies. Different from general precision manufacturing approaches, the two-photon method has intrinsic three-dimensional (3D) processing capability with a reasonable spatial resolution around 100 nm. It is potentially a technical route to fabricate 3D multifunctional devices and their spatial integrating system. Here we introduce its use in fabrication of micro-nanophotonic, mechanical and meta-material structures [1-20].

We report the two photon luminescence (TPL) and second harmonic generation (SHG) characteristics of Zinc Oxide (ZnO) in ceramic, thick film and nano-rod. All samples were prepared from commercially available analytical pure ZnO powder. Sintering, physical vapour deposition (PVD), and hydrothermal methods were used in preparing the three types of samples respectively. The comparison among the three showed, while a degree of similarities between the ceramic and the nano-rod, a significant difference in the film. Possible reasons for the wavelength downshift in the film sample are discussed. Images acquired by TPL and SHG microscopy are presented, both ceramic and film samples show granular structure and a reverse bright-dark contract was observed from TPF to SHG image between the grain region and the granular boundaries.

Both degenerate and nondegenerate two-photon absorption (2PA) spectra are studied in two different samples of CdTe quantum-dots in borosilicate glass hosts. One sample (CdTe-600) contains quantum-dots of radius 3.2 ± 0.2 nm and has its absorption edge at 600nm. The other sample (CdTe-750) contains quantum-dots of radius 6.6 ± 0.9 nm and absorption edge at 750nm. CdTe-600 contains quantum-dots with a narrower size distribution than CdTe-750. Consequently, the peaks corresponding to discrete transitions are more clearly visible in CdTe-600 than in CdTe-750. Both nondegenerate and degenerate spectra for these samples show a marked difference from bulk CdTe. In CdTe-750 the two-photon absorption spectrum has a shape similar to that for bulk solids but for CdTe-600 the 2PA spectrum is somewhat different from that expected for the bulk. In the Z-scan measurements we also observed a photo-darkening effect, which is accompanied by an increase in the measured effective 2PA coefficient. All results suggest that 2PA cannot be predicted by the bulk theory especially near to the 2PA edge, that the 2PA in quantum dots is generally smaller than would be expected for the same volume of bulk semiconductor with the same band edge, and that the quantum-dot size and size distribution play important roles in the 2PA spectral behavior and magnitude.

It is well known that "vector" diffraction theory needs to be invoked to describe the propagation of light through apertures having dimensions on the order of the wavelength of light. For regions close to the aperture, use of Kirchhoff boundary conditions in the aperture plane is invalid. The Hertz vector formalism provides a way to describe the diffraction of light beams through apertures having sizes ranging from half the wavelength of light to larger values. Here we will present a summary of the method used to calculate the distribution of all of the electromagnetic field components and a Poynting vector component at and near the plane of a single elliptical aperture.

Spectroscopic observations are presented for carbon nanotubes grown on silicon and quartz substrates in a hexagonal honeycomb configuration using self-assembly nanosphere lithography and plasma enhanced chemical vapor deposition method. A white light source is used as an incident beam and light reflected from the surface of the carbon nanotubes results in a distinctive signature in the reflected spectrum. A comparison of non-periodic arrays and periodic arrays of carbon nanotubes show that the reflectance signature is only observed when the carbon nanotubes are oriented in a periodic array. Further observations regarding the light antenna effect observed in nonperiodic arrays are also reported. Theoretical curves show good agreement to experimentally observed phenomena. The unique optical properties of the arrays combined with the excellent mechanical and electrical properties of carbon nanotubes indicate that these materials may find many uses in the field of optoelectronics.

Light-emitting nanofibers grown from organic molecules such as para-hexaphenyl or substituted para-quaterphenyl have extraordinary morphological, optical and electrical properties that make them interesting candidates as key elements in future electronics and photonics. These fibers are generated in a self assembly fashion on template substrates. In order to integrate them into more complex structures, a transfer from the growth substrate is necessary. In this paper we show results from optical and morphological measurements on nanofibers transferred onto semiconductors, kept freely floating in solution and frozen in gel. The former investigations allow us to study with nanometric resolution via an atomic force microscope the deformability of nanofibers. The latter studies, based on single photon as well as confocal two-photon microscopy, provide three-dimensional optical images and also the angular distribution of light emitted from individual aggregates. It is observed that waveguiding affects the spatial emission characteristics.

The method of electrophoretic deposition of charged polymer (polystyrene) microspheres on topologically patterned substrates is discussed. Surface patterning with different symmetries and structure periodicity in the sub-micrometer range over large surface areas was realized by laser interference lithography. Growth of colloidal crystals on patterned and bare electrode surfaces was compared. Surface patterning predetermined the colloidal crystal structure and orientation. Fcc colloidal crystals with (111), (100) and (110) crystal plane orientations parallel to the electrode surfaces were successfully grown on patterned electrodes with the corresponding pattern symmetry. The growth of colloidal crystals with (111) and (100) crystal plane orientations parallel to the electrode surface was easily controlled by patterned surfaces, while only two layers of colloidal crystals having the (110) plane orientation parallel to the electrode surface were grown in a controlled way. The growth of thick colloidal crystals in the non-close-packed [110] direction generated a mixture of small domains of different orientations, where domains with (111) and (100) orientations dominated. The thickness of the colloidal crystals was controlled by varying the deposition parameters. Thickness increased with increasing the applied voltage, deposition time, concentration of colloidal particles and with decreasing the withdrawal speed of the electrodes from the colloidal suspension. A threshold voltage of 3.36 V was determined, beyond which a significant increase in the thickness of the colloidal crystals with applied voltage was observed. A gradient in the thickness of the colloidal crystals was obtained across the electrode surface at low withdrawal speed (0.04 mm/s). Colloidal crystals with a homogeneous thickness over the electrode area were formed at withdrawal speeds of 0.07 - 0.1 mm/s.

The quest for applying optical tweezers system for novel applications has aggrandized its trapping capabilities since its inception. Researchers have proposed and applied light based micro-manipulation technique in the field of colloidal sciences, bioscience, MEMS and the count is limitless. In this paper we report the self-imaged optical bottle beam based optical tweezers system. A self-imaged bottle beam possesses three-dimensional intensity-null points along the propagation axis. The transverse intensity profile of the self-imaged bottle beam oscillates along the propagation axis, hence providing three-dimensional trapping potential for high and low indices microparticles at constructive and destructive interference points, respectively. Bottle beam based optical tweezer system adds the beneficial property of Gaussian and Bessel beam based trapping systems by providing three-dimensional trapping potential and self-reconstruction ability, respectively. As self-imaged bottle beam belong to the family of propagation-invariant beams, it can be used to trap chain of high and low indices microparticles three-dimensionally along the propagation directions, which can be used to periodically stack microparticles (of different refractive index) longitudinally.

We have developed a new type of hybrid organic-inorganic materials constituted of organic nanocrystals embedded in silicate matrices. They are prepared by a generic process based on the confined nucleation of molecular crystals in the pores of sol-gel matrices, bulk or thin films. In this study, we have controlled the spatial distribution of organic nanocrystals in sol-gel thin films prepared by spin-coating. This spatial control of nucleation is obtained by assisting the nanocrystallisation process through nanostructured substrates. Substrates exhibit arrays of wells where the dye nucleates when the initial solution is deposited. The 3-D spatial control is achieved through a multilayer process. This nucleation control gives an opportunity to design new 3-D optical data storage or 2-D arrays of luminescent crystals for chemical or biological sensor applications.

Optical studies of porous nano-engineered thin film materials fabricated using Glancing Angle Deposition (GLAD) have been a focal point of research since the inception of the GLAD technique over ten years ago. As the sophistication of porous nano-engineered thin film designs has increased over the years, photonic device applications of these materials have been explored. We will review some of our recent advancements in the study and fabrication of porous nano-engineered thin films for optical applications including our group's work with helical films and devices, square spiral photonic crystal films, and graded-index (GRIN) films and devices. Initial optical studies of helical films focused upon the circular Bragg effects and optical rotatory dispersion exhibited by such structures. In recent years, the exploration of different materials and the fabrication of liquid crystal (LC) cells using these films have brought the prospect of using such film-LC hybrids in display applications much closer. Helical films made from luminescent materials have also been investigated and were found to emit partially circularly-polarized light. Our work with square spiral structures focuses upon the fabrication of periodic arrays of such structures in order to yield a three-dimensional photonic bandgap. Our techniques also enable the formation of designed defects in the array with relative ease, opening the door to a myriad of potential applications. Finally, we will discuss graded-index structures which are made by varying the porosity of the film structure during film growth. Films of this nature have been designed and fabricated for use as wide-band antireflection coatings, rugate filters, spectral-hole filters, and optical humidity sensors.

The hydrogenated Silicon nitride film is well developed to form a passivation layer for non-volatile memory devices. It has many superior chemical, electrical, and mechanical properties. In addition, it also has excellent optical properties. It is transparent in UV and DUV range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a hydrogenated silicon nitride (SiN_XH_Y) membrane as an optical phase element. By using e-beam lithography, we demonstrate on feasibility for the fabrication of subwavelength optical elements, such as waveplate, polarizer, and polarized beam splitter on a silicon-based low stress SiN_XH_Y membrane for the UV region applications. An SiN_XH_Y film was deposited by plasma enhanced chemical vapor deposition (PECVD) and the free- standing membrane is formed by KOH silicon backside etching, from which substrate materials are removed. The membrane's morphology and geometries of subwavelength optical elements were verified by means of an scanning electron microscope (SEM), and the optical performance characteristics of these subwavelength optical elements are shown. The experimental datas agree well with theoretical predictions.

In this paper, fabrication an optical filter based on guided-mode resonance (GMR) effect in a silicon nitride (SiNx) membrane by silicon bulk micromachining technologies is demonstrated. Such a filter has advantages of simple structure, high efficiency and it is potential to be integrated with other developed optoelectronic elements into an integrated micro systems. The design consideration, fabrication procedures and measured spectral response are shown in this paper.

A recently proposed THz laser concept in homoepitaxially grown p-Ge with layered doping is reviewed. Prospects for realizing a similar design in Si or GaAs are considered.

Different types of objective lens (OL), i.e. circular, annular and one-dark-ring, are proposed and demonstrated to control the aspect ratio (AR) of micro-focus-region of high numerical aperture (NA) OL. Namely, the AR decreases from about 7.3 to 2.7 in case of using a circular OL with NA changes from 0.7 to 1.4, respectively. By using an annular OL, the transverse size of the focal spot of micro-focus-region decreases but its longitudinal size increases, so that the AR increases several times with respect to the case of circular OL. In particular, when using the one-dark-ring OL, one can decrease both transverse and longitudinal sizes of the focal spot or decrease only the longitudinal size, so that the AR obtained with a one-dark-ring OL is decreased to about 70% of that obtained with a circular OL. Such lenses can be useful for many applications such as sub-microfabrication and three-dimensional data storage using multi-photon absorption process.

A method for fabrication of nano-scale GaN structure by inductively coupled plasma etching is proposed, exploiting a thermal dewetting of Pt thin film as an etch-mask. The nano-scale Pt metal islands were formed by dewetting of continuous film on SiO₂ dielectric materials during the rapid thermal annealing process. For the Pt films with thickness of 30 nm, temperatures of > 600°C initiate pattern formation and the dewetting of Pt films. Controlling the annealing temperature and time as well as the thickness of Pt metal film could manifest the size and density of Pt islands. The activation energy for initiation of Pt metal dewet was calculated to be 23.2 kJ/mole. The islands show good resistance against dry etching using CF₄ based plasma for dielectric etching, indicating that the metal island by dewetting of thin film is suitable for etch mask in the fabrication of nano-scale structures. This fabrication method was also proven to be effective in the fabrications of GaN nanocolumns with widths as small as nanometer scale.

SU8 is a commercial negative photoresist, which is highly transparent in the visible and near-infrared and extremely resistant to many organic solvents. Here we show that sub-micron period diffraction gratings, and 2D photonic crystal structures, can be readily formed holographically over extended areas. By coating the SU8 layer with a suitable gain medium, such structures may be used as feedback and output-coupling gratings for organic waveguide lasers. Thin films of SU8, were initially deposited by spin casting onto glass substrates. These films were then mounted in one arm of a Lloyd's mirror interferometer and exposed with the expanded beam of a HeCd laser, operating at 325 nm. Subsequent baking and developing steps lead to both volume gratings with index contrast of 0.014, and surface gratings with corrugation depths of up to 140 nm. By varying the incidence angle of the HeCd laser beam to the SU8 film we have tuned the microstructure period from 500 nm down to 200 nm. Using multiple exposures, both doubly-periodic diffraction gratings and square-lattice crystal structures have been produced.

A technique for the fabrication of colloidal gold nano-wire and nano-dumbbell shaped particles using carbon nanotubes and rod shaped viruses as templates is described. The gold (Au) encapsulation process was accomplished by the precipitation of gold chloride from aqueous solutions. When this process was conducted in the presence of hydroxylated C₆₀, small pieces of phase-separated composites of AuC₆₀ appeared to have formed. These nano-clusters may turn out to be large noble metal analogs of the alkali metal fullerides with the smallest geometrically possible Au aggregate consisting of 55 gold atoms. The existence of noble metal fullerene composites has been previously theorized. The alkali metal fullerides are examples of phase separated solids and have exhibited superconductivity with temperatures as high 33K. The mechanism required for the binding energy between C60 and gold has been observed to exist between C₆₀ and many of the mirror metals (Al, Ag, Au, Cu, Ni). This binding energy is a charge transfer from the metal Fermi level into the C₆₀ LUMO. If this bonding energy, is greater than the metals coagulation energy an Au/C60 size terminated mechanism during the formation of the gold aggregates by the adhesion of C60 to the surface is energetically favorable.

Thin films with chiral or helical microstructures exhibit circular birefringence effects. Glancing angle deposition (GLAD) is a fabrication method capable of producing chiral thin films with controllable porosity and microstructure. In this paper, the effects of porosity on the circular birefringence exhibited by helical TiO₂ films are presented. Transmittance measurements reveal two optimal film growth angles: one corresponding to a maximum in form birefringence and another corresponding to strong anisotropic scattering. Reflectance data support the transmittance measurements in the regime where scattering is minimized.

The photoconductivity spectra of the structure nanodimensional Ge/c-Si with Ge quantum wells on a single-crystal substrate surface were measured using infrared spectrophotometer IR-12. The same measurements were also made for the structures Al0.2Ga0.8As/In0.1Ga0.9As/GaAs with further comparison of received results to standard GaAs photodiode. The photoconductivity spectrum of nanodimensional Ge/c-S i structure was received at room temperature. The investigated samples are made by molecular - beam epitaxy method. rectangular frame type (5x5 micron) contact was generated on a surface of Ge layer. The thickness of a contact strip was equaled to 0,5 micron. The second contact was soldered to the back side of the singlecrystal surface. A shifting voltage U =1,5 V was switched in the opposite direction (negative potential to Ge slice) At measurements of photoconductivity of structure. It is necessary to note that photoconductive signal was 3 orders less, than at inverse displacement. It specifies presence heterotransitions between Ge and c-S i layer. The photosensitivity of a standard silicon photodiode was investigated for comparison of such assumption. For example the spectral dependence of photosensitivity of standard silicon photodiode FD-142Κ is represented. The spectral position of a photoconductivity curve was the same to standard silicon photodiode at room temperature. The value of photosensitivity of a researched sample was compared with the standard photodiode. Is established, that both these values are of the same order. It is possible to explain it by presence of a potential barrier between Ge and Si. It is known that longwave border of photoconductivity is defined by width of the forbidden zone of the semiconductor. The increase of photoconductivity is caused by increase of absorption at rising of quantums energy of the exited radiation (at reduction of wavelength). The form of a photoconductivity spectrum of the photodiode FD-142Κ and absence of a hole in the spectrum in short-wave area (1,5-2,1 μm) specifies that the speed of a surface recombination is equal to zero. For the structure nanodimensional Ge/ c-S i, otherwice, significant hole in this area was observed at the room temperature. So, samples had the large speed of surface recombination. To observe the contribution of nonequilibrium charge carriers to the photoconductivity of structure nanodimensional Ge/c-Si it is necessary to cool down to Τ < 100 K. The intersubband transitions can occur in nanodimensional Ge at such temperatures. So, it is necessary to expect observation of a photosensitivity in the infrared, which corresponds energy of these transitions. It is possible to explain photosensitivity of nanostructures by existence of interzoned transitions in nanodimension Ge. The spectral dependence of photosensitivity of structure nanodimension Ge/c-Si in IR- of area is received. Analysis of received results have shown that the spectrum Al0.2Ga0.8As/In0.1Ga0.9As/GaAs differs from standard GaAs photodiode by wider spectral sensitivity range owing to creation of nanodimensional layers Al0.2Ga0.8As/In0.1Ga0.9As on the GaAs substrate. It gives the possibility to detect optical irradiation.

Imprint lithography has been proposed as a low cost method for next generation lithography for the manufacturing of semiconductors for the 45nm node and below, as costs for traditional optical lithography, and EUV lithography escalate to new levels that may prohibit new semiconductor devices from ever coming to market. While this was the widely proposed use of this technology, a whole host of new areas can take advantage of this lower cost manufacturing technology. MEMS devices that can be scaled to smaller dimensions, construction of nano-optical devices for OLED applications, biosensors, light dispersion gratings and many other types of devices in need of nanometer scale fabrication. The template enables imprinting all these devices. Template manufacturing and development is currently done along side of state of the art reticle manufacturing. While the dimensions of the 1X templates is significantly smaller than what is needed for optical lithography templates, the dimensions are on the same order as the optical assist features, scatter bars and serifs used today. We will show current capability of 1X templates for imprint applications that are available commercially today, for semiconductor and nanofabrication applications.