We have developed nanoimprint technology to fabricate functional optical components. The future and usage of various molds for nanoimprint are described and their patterning examples are shown. Several applications of the nanoimprint technology are introduced; anti-reflection surface structure by using graded convex and concave patterns, extremely low threshold dye laser by 2-dimensional photonic crystals infiltrated with a gain medium, and various semiconductor nanostructures being used for functional optical devices. Nanoimprint is key technology to realize these components.

This paper reports a new microfabrication process named "Multi-Scale Soft-Lithographic Lift-Off and Grafting (MS-SLLOG)" used to construct active nanophotonic devices. MS-SLLOG is a low-temperature (less than 150°C) microfabrication technique that allows soft lithographically molded polymer micro-structures to be integrated together with silicon-based microelectromechanical systems (MEMS) structures to perform active control. Moreover, MS-SLLOG process allows us to achieve a hierarchical device structure seamlessly accommodating feature sizes ranging from tens of nanometer to sub-millimeters on a single chip for nanophotonic structure integration. To demonstrate the MS-SLLOG process capability, a strain-controlled micro-optical grating device is fabricated and experimentally characterized. The experimental results successfully show the operation of an active polymer nanophotonic device fabricated by the MS-SLLOG process.

Using microstereolithography technology based on dynamic pattern projection, we can fabricate micro parts with high aspect ratio. In this technology, STL file is the standard format as the same of conventional rapid prototyping system, and 3D part is fabricated by stacking layers that are sliced as 2D section from STL file. In the conventional method, the resin surface is cured as scanning laser beam spot according to the section shape, but in this research, we use projection process which enables to cure the resin surface by one irradiation. DMD is a dynamic pattern generator that makes black and white regions according to bitmap image generated from sliced section. In this paper, we deal with the operation of dynamic pattern generator, fabrication of microstructures, and curing characteristics. Firstly, we mention microstereolithography apparatus and process including optically designed position and rotation of lenses, mirrors, and DMD according to light path. Secondly, we examine curing characteristics between exposure time and curing depth and width. Thirdly, we consider optimal exposure pattern such as several exposures instead of one exposure with the same exposure time. This enables the part fabricated more accurately because of not excessive but proper energy delivery to the resin surface. Finally we verify this system by fabricating micro part with high aspect ratio and complexity.

We developed a Fabry-Perot (FP) optical modulator with electro-optic (EO) films fabricated by aerosol deposition (AD). We found the ferroelectric Pb(Zr,Ti)O₃ film by AD produced a fairly high EO coefficient (>150 pm/V), approximately 10 times larger than that of LiNbO₃. Since thick EO films greater than 5 μm can be deposited on a transparent electrode layer or a metallic mirror layer of the FP optical modulator by AD, the FP optical modulator can achieve low capacitance, resulting in high modulation speed. Transmittance spectra of the FP optical modulator coincided with the optical simulation spectra, which indicated that optical scattering in AD films and at the surface/boundary were very small. We demonstrated an optical intensity modulation with applied electric field to EO film of ferroelectric Pb (Zr, Ti)O₃. We obtained a 4-dB modulation with 50 V for the 10-μm-thick modulator with dielectric multilayer mirror on a glass substrate.

This paper describes a new fabrication process of a micro elliptical collimator lens to form a beam shape for LD(Laser Diode), and the evaluation results of the optical characteristic for this lens. Beam shape of LD is an ellipse because divergent light angle is different between horizontal and vertical direction, which increases a coupling loss with an optical fiber. In this presentation, we propose the lens to form the divergent light of an elliptical beam shape to the collimated light of a circular beam shape. This lens makes it possible to reduce the coupling loss with the optical fiber. For this purpose, we designed one lens, which has different curvature radiuses between incident and output surfaces. In the incident surface, the divergent light is formed to the convergent light, and in the output surface, the convergent light is formed to the collimated light. We simulated the optical characteristic of this lens, and designed for various parameters. In order to fabricate this lens, we propose a new process using a chemically absorbed monomolecular layer, which has an excellent hydrophobic property. This layer is patterned and deposited by a photolithographic technique. Next, we drop a UV(Ultra Violet) cure material on the hydrophilic area, as the result, we can fabricate a micro elliptical lens shape. The curvature radius of this lens can be controlled by the amount of a dropped UV cure material and an elliptical pattern size in horizontal and vertical direction. The formed lens shapes are transferred by the electro-plating and then the micro dies are fabricated. And they are used for molding the plastic lens.

Near-field optics is one of super-resolution techniques for future data storage system. We have already proposed a near-field optical flying head with a circular aperture. Realizing higher performance aperture, we also have developed a triangular one which has been experimentally evaluated with scanning near-field optical microscope probe. In this paper, we demonstrate readout performance of this novel aperture mounted near-field head introducing polarization control. In order to scan over a media surface at small spacing condition, we fabricate a "contact" type head having contact pads and a polarization maintaining fiber, because this type of an aperture can only effectively function on condition both of extremely small spacing and applying polarized light. The contact pads and the tip are formed by photolithography with hydrofluoric acid (HF) solution. An aluminum film is formed on the tip. The aperture is formed by squeezing the shading film. Measurement of surface configuration by an interferometer shows that the aperture and the contact pads are almost on the same plane within 5 nm deviation. The media consists of a glass substrate, a titanium layer, a carbon protective layer, and a lubricant layer in sequence. Line-and-space (L&S) patterns whose width are 40~200nm are formed on the titanium layer. The contact head approaches the media surface, and then the media is scanned by a piezo stage. The near-field light generate from the triangular aperture is scattered by the L&S pattern and detected by a photomultiplier tube. Signal readout from the 40-nm-wide L&S pattern is demonstrated.

This paper gives a comprehensive and up-to-date review of our research activity on MEMS (micro electro mechanical systems) for all- optical fiber optic communications. Micromechanical approach for handling optical signal has advantages over solid-state devices in terms of high contrast intensity modulation by relatively large change of refractive index, large spatial scan angle by optomechanical reflection or refraction, and optical transparency in wide range of wavelength. MEMS also has industrial impact in a sense that it could potentially eliminate or cut down the cost of optical assembly thanks to the optical pre-aligning or self-aligning capability. In particular, we take an example of MEMS variable optical attenuator (VOA) that we have commercially released in cooperation with an industrial partner. Besides fiber optic MEMS, we also mention other applications such as projection displays using a high-speed MEMS optical scanner for scanning modulated laser beam to create images. Furthermore, we also introduce a MEMS color pixel based upon the mechanically tunable Fabry-Perot interferometer made of two plastic films; the color pixel can be assembled in an array format to create a transparent-type over-sized electronic poster which is mechanically flexible and electrically rewritable.

Reconfigurable wideband photonic networks based on dense wavelength division multiplexing (WDM) are promising for versatile ubiquitous services. In such networks, wavelength-selectable optical switches will be needed for WDM-based routing, which is a primary function of the networks. A critical requirement is a wavelength selection time of 20 ms or less; otherwise, data packets will be lost. Various filters, including acousto-optic filters or Fabry-Perot etalon filters, are candidates for such switches, but all are inadequate because of high driving power or low accuracy in selecting wavelengths. We propose and demonstrate a wavelength-selectable switch that consists of micromechanically movable in/out filters. A series of thirty-two in/out elements with highly wavelength-managed dielectric filter units, which have flat-top spectral responses according to ITU-T grids, are densely packaged into a small space of 45 x24 x11 mm using miniaturized voice-coil motors (VCMs). By accurately arranging the filter elements along a collimating optical beam between fibers, we achieve small total insertion losses of less than 2.5 dB for all elements. By optimizing the VCM torque, we also achieve a wavelength-selection time of 10 ms (The minimum is 5 ms). We also achieve good wavelength reproducibility with an error of less than 0.1 nm, which was confirmed by a repetition test. These results show that the proposed switches are suitable for practical use.

Volume holographic recording is a promising solution for next- generation optical disc storage that has a high capacity more than 1 TB. This huge capacity is achieved by superimposing many holograms, each of which has millions of bits, at the same recording spot. We proposed a new technique, Spatial Spread Spectrum (SSS) multiplex recording. Unlike conventional multiplex holography based on Bragg effect of thick holograms, our technique utilizes spatial phase modulation and demodulation of the signal beam itself with a random diffuser to address the multiplexed page data. SSS multiplexing is additionally combined with other multiplexing methods, and provides further improvement of the total capacity of holographic storage. In this paper we experimentally verify the basic recording and readout feasibility, and investigate the shift selectivity and the aligning margin of the SSS holographic recording that are an important factor to determine the tolerance against vibration. It is shown that a clear 2-dimensional image is successfully reconstructed from the hologram even in the case the central part of the diffused signal beam is blocked in recording, and that a sharp shift selectivity about 5 microns was obtained by a diffuser with a diffusion angle of 15 degree, and the aligning margin for a sufficient SNR was approximately 1 micron.

Recently, there are a lot of studies on the micro motors using an electrostatic actuator as the driving force in the micro electro mechanical systems (MEMS) field. However, the electrostatic actuator has a problem concerning the precise actuation control. In the conventional researches, the rotary type electrostatic actuators have been reported, but the rotation angle has not been precisely controlled in the actuators. This paper describes a new micro motor by a rotary type scratch drive actuator (SDA) with a Poly-Si scale to measure the rotation angle based on the MEMS technology. In this study, we make it possible to measure the rotation angle of th rotary type SDA motor by a fiber type micro encoder. For this purpose, we formed the Poly-Si scale around the outside of the micro SDA motor, and achieved a reflection type optical fiber micro encoder. In this presentation, we describe the fabrication process for this device and the evaluation results of the optical characteristic of the fiber type micro encoder.

We report on a channel-drop filter (CDF) with a mode gap of propagating mode for a photonic crystal slab that was fabricated on silicon on an insulator wafer. The results simulated with 3-dimensional finite-difference time-domain and plane-wave methods demonstrated that an index-guiding mode for a line defect waveguide of a photonic crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector for the propagating light-wave through the line defect waveguide, and it can be used as an optical filter. The filter bandwidth was varied from 1 - 8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550 - 1600 nm. We fabricated a Bragg reflector with a photonic crystal line-defect waveguide and with Si-channel waveguides and obtained results of transmittance abrupt dips that come from the Bragg reflector that were measured in the transmittance spectrum. The experimental results are consistent with our theoretical analysis.

Recent rapid progress in a digital network society necessitates storage devices with higher-density and faster transfer rates. In optical storage, a novel recording principle is eagerly awaited that will drastically improve recording density without being restricted by a wavelength shortening limit or a numerical aperture (N.A.) limit of the optics utilized. Storage based on the "near-field" principle is thought to be one of the most promising breakthroughs for overcoming various tough limitations governing traditional optical recording. From this perspective, we have already proposed an integrated optical head slider assembly that relies on the novel near-field principle for its operation; it is mounted on a minute tapered aperture and has a planar focusing lens and a micro silicon mirror. Readout signals corresponding to a 200-nm-long bit have demonstrated a frequency band up to approximately 10 MHz, using a chromium patterned medium. In this study, we have investigated a tribological (glide height) property and flying stability of a miniaturized 1.5-mm-long optical head slider by using acoustic emission sensor signal and readout signal from the medium. We have also evaluated detecting performance separately using traditional 3.2-mm-long slider and a chromium patterned medium whose bit patterns are accurately scored with bit lengths less than 100 nm using electron beam lithography including reactive ion etching. We have confirmed stable flying performance of 1.5-mm-long slider assembly and furthermore, ability of detecting sub-100-nm long bit patterns.

We measured the size and temperature dependence of the optical nonlinear cross section (σ_eff), the carrier recombination time (τ), and the dephasing time T₂ using CdS_0.12Se_0.8 microcrystallites embedded in alkaline multicomponent glasses and CdSe microcrystallites embedded in SiO₂ thin film using the folded-boxcar configuration of degenerate-four-wave-mixing. As the average radius of a CdS_0.12Se_0.8 microcrystallite decreased from 10 to 1 nm, the values of σ_eff and the carrier recombination time changed from 2.6x10^-16 to 1.1x10^-16 cm² and from 70 to 2 psec, respectively. The smaller a microcrystallite was, the faster the carrier recombination time became. The size dependence of the carrier recombination time showed that an energy level structure of microcrystallites with a radius of less than a few nanometers is a two-level system, for which it was theoretically known that σ_eff was proportional to T₂. The size and temperature dependence of T₂ for the CdS_0.12Se_0.8 microcrystallites revealed the presence of the acoustic-phononassisted relaxation processes different from the pure-dephasing processes in the dephasing processes. The dependency indicated that longer T₂ might enhance σ_eff. We investigated the enhancement for a nonlinear cross section in CdSe microcrystallites embedded in SiO₂ thin film by becoming longer T₂. The carrier recombination time, σeff, and T₂ of the 3-nm-average-radius CdSe microcrystallites embedded in a SiO₂ thin film were 40 psec, 4.5x10^-15 cm², and 150 fsec. The σ_eff was ten times as large as σ_eff for the 3-nm-average-radius CdS_0.12Se_0.88 microcrystallites embedded in alkaline multi-component glasses. The T₂ was ten times as long as the extrapolated value for the same size CdS_0.12Se_0.88 microcrystallites doped in the glasses. We conclude that the longer T₂, originated from the changing of the surface and interface, enables the enhancement.

Unique measurements setup has been designed to examine the fiber-length-dependent energy conversion in multi-core-type photonic crystal fibers (PCFs) at the illumination of femto-second Ti-Sapphire laser pulses. Gradual spectral change of some peaks generating through 5 m-long PCF has been observed by using this system. Those peaks and their shifts have been identified as solitons and soliton self-frequency shift. On the other hand, the origin of peaks in shorter-wavelength regime is neither dispersive waves which are emitted and trapped by solitons nor idler waves generated by four-wave mixing or sum-frequency shift. Wavelength dispersion profiles of 5m-long PCF have been determined by measuring chromatic dispersion using a spectroscopic streak camera and the supercontinuum light, which is generated from a 20-mm-long PCF under illumination of a femto-second Ti-sapphire laser pulse.

Recently DNA molecules have been focused on as electronic elements in the field of nanometer-scale electronics. One of the fundamental issues in this research area is the development of methods to measure accurately an electrical conductivity of DNA wire. The DNA tweezers we have recently developed have a great advantage of measuring the electrical current passing through DNA wire. In this paper, we investigated the electric conduction of lambda DNA molecules covered with Pd colloids using micromachined DNA tweezers that has a pair of opposing probes for retrieving DNA molecules. The molecules were retrieved from a solution containing lambda DNA by applying RF power between the probes in the solution. The retrieved molecules were then soaked in a colloidal solution containing cationic Pd particles, which results in a DNA-Pd wire bridged between the tweezer probes. Current-voltage curves for the DNA-Pd wire can be measured between the DNA tweezers probes, and the resistivity of the DNA-Pd wire was approximately 74 Ωcm. We found through an observation by a scanning transmission electron microscope (STEM) that the surface of the wire was covered by Pd particles closely. We also measured the piezoresistance through a change in the distance between Pd particles on a DNA-Pd wire using the DNA tweezers.

Protein motors are enzymes that naturally generate force and move along tracks of protein polymers (actin filaments or microtubules), using energy from the hydrolysis of adenosinetriphosphate (ATP). To harness these protein motors to power nanometer-scale devices, we have investigated effective and non-destructive methods for immobilizing protein motors on surfaces and to arrange the output of these motors, e.g. force and movement, to be in a defined direction. We found polymethylmethacrylate (PMMA) and NEB-22 to be useful for immobilizing protein motors while retaining their abilities to support the movement of protein polymers. We fabricated various patterns of tracks of PMMA or NEB22 on coverslips and protein motors were introduced and immobilized on the patterns. The trajectories of protein polymers were confined to these tracks. Simple patterns readily biased polymer movement confining it to be unidirectional. Applications of motor proteins in nanometric fine-movement microactuators are now stepping closer to reality.

This paper proposes a new method for detecting label-free T4-DNA molecules using a Surface Plasmon Resonance (SPR^1,2) technique on a gold thin film. We used a solution that dissolved T4-DNA molecules in pure water, and examined the relation between DNA concentration change and SPR angle change in the solution. As the result, it was confirmed that the SPR angle change increased with the increase of the DNA concentration change. Therefore, it was feasible to detect the DNA concentration change using the SPR technique. Further, in order to examine to detect a single DNA molecule, we calculated the area that a single DNA molecule would occupy in SPR area, and we examined to focus the beam of the SPR device at the area. However, it is difficult to focus the diameter of the spot within 500um because ofn the size of a light source and the incident angle of the light. Therefore, we tried to fabricate the SPR chip in which SPR area is narrowed that has the same effect as focusing the beam. In order to narrow the SPR area, we decreased the area of gold thin film in this chip, and also, in order to reflect a light from only the area of gold thin film, the area without a gold thin film was micro-machined to make it unevenness for the reduction of a light reflection. By the above-mentioned method, we examined the possibility to detect the label-free DNA molecule using the SPR technique.

Numerous equally-spaced emission lines can be generated by stimulated Raman scattering and subsequent four-wave Raman mixing. The spectral domain extends from the near-infrared to the deep-ultraviolet, and then an ultimately-short optical pulse can be generated by phase locking in the process of four-wave Raman mixing. In fact, an intense 17-fs optical pulse has been generated using this technique. A comb of 1.6-fs optical pulses, i.e., the shortest optical pulses, has also been generated by other researchers. On the other hand, it is possible to generate highly-repetitive pulses using a continuous wave (CW) laser as a pump source and molecular hydrogen as a Raman medium in a high-finesse cavity. Coherent superposition of the two-color beam comprising of the fundamental beam and the Stokes beam provides a sinusoidal wave modulated at 17 THz. It is also possible to generate more than three emission lines simultaneously, which should generate an impulsive wave. It is noted that such Raman emission can be generated in a hollow-core fiber, making the device extremely simple. Such a device may have a potential for use in basic science and technology, e.g., the generation of a three-primary-color laser for display.

We have studied the generation of terahertz (THz) waves by optical parametric processes based on laser light scattering from the polariton mode of nonlinear crystals. Using parametric oscillation of LiNbO₃ or MgO-doped LiNbO₃ crystal pumped by a nano-second Q-switched Nd:YAG laser, we have realized a widely tunable coherent THz-wave sources with a simple configuration. We report the detailed characteristics of the oscillation and the radiation including tunability, spatial and temporal coherency, uni directivity, and efficiency. A Fourier transform limited THz-wave spectrum narrowing was achieved by introducing the injection seeding method. Further, we have developed a spectroscopic THz imaging system using a TPO, which allows detection and identification of drugs concealed in envelopes, by introducing the component spatial pattern analysis. Several images of the envelope are recorded at different THz frequencies and then processed. The final result is an image that reveals what substances are present in the envelope, in what quantity, and how they are distributed across the envelope area. The example presented here shows the identification of three drugs, two of which illegal, while one is an over-the-counter drug.

Nitride-semiconductor technologies for blue lasers are reviewed. Nitride semiconductors from GaN to InN are covered with respect to MOVPE growth and characteristics. For GaN, two-step growth significantly improves crystalline characteristics, such as the concentration of residual carriers, mobility, and surface morphology. For InGaN, a key material for the emitting layer of blue lasers, the use of nitrogen as the carrier and bubbling gases for metalorganic sources enhances indium incorporation, and composition control has been achieved. The phase separation of InGaAlN system has been semiempirically predicted using the strictly regular solution model. As substrates for the epitaxial growth, a several materials are discussed along with the affect of the substrate polarity on the characteristics of epitaxially grown GaN. P- and n-type doping are also briefly examined. Looking at future prospects for blue lasers, the effect of polarization in device structures and the bulk-crystal growth for substrates are described.

Negative dielectric planar waveguides is reviewed toward silicon nanophotonics from the point of view of two-dimensional optical waves. Excitation, index-guiding, squeeze of optical beam width, adiabatic mode conversion of two-dimensional optical waves are discussed theoretically. The efficient excitation method of surface plasmon polariton is proposed as an adiabatic coupler from optical fibers. This is a gateway from conventional dielectric waveguides to nanophotonics. Low-dimensional optical waves at exotic interfaces are studied for the interface including non-metallic negative dielectrics, negative permeability materials and left-handed materials. Future perspectives toward polaritonics is discussed.

Waveguide-based surface plasmon resonance (SPR) sensors are analyzed using both 2-D and 3-D beam-propagation methods and the sensing characteristics are discussed for aqueous environment. First, the effect of the metal thickness on the sensing characteristics is investigated. It is shown that the maximum absorption wavelength shifts to a longer wavelength, as the metal becomes thick. Next consideration is given to the SPR sensor with the adsorbed layer placed on the metal layer. The change in the adsorbed layer thickness also leads to the shift of the maximum absorption wavelength. The reason for the wavelength shift is explained in detail using the eigenmode analysis. The configuration parameters are determined for the sensor operation around a wavelength of 0.6 μm. As a result, the sensor shows the absorption wavelength shift from 0.594 to 0.602 μm, when the refractive index of an analyte is increased from 1.330 to 1.334. Finally, the numerical results of the 2-D model are compared with those of the 3-D model.

We have fabricated a polymer solid-state microstructure for optical application by two-photon-induced polymerization technique. The photopolymerization resin contains conventional laser-dye and dendrimer. A dendrimer can encapsulate the laser-dyes, limiting cluster formation and intermolecular energy transfer, and promising a high level of optical gain. The effect can be extended to prepare an optically active microstructure using the two-photon-induced polymerization technique. We fabricated a polymeric microcavity, which consisted of <400 nm-linewidth strips arranged in layer-by-layer structure. The periodic variation in the refractive index gave rise to Bragg reflection. A laser emission was measured in the microcavity under optical excitation. The spectral linewidth was about 0.1 nm above the lasing threshold. We investigate both the material functions in the molecular scale and controlling the device structure for desired applications such as a polymer DFB and photonic crystal.

In recent years, reversible logic has emerged as a promising computing paradigm having its applications in low power computing, quantum computing, nanotechnology, optical computing and DNA computing. The classical set of gates such as AND, OR, and EXOR are not reversible. Recently, it has been shown how to encode information in DNA and use DNA amplification to implement Fredkin gates. Furthermore, in the past Fredkin gates have been constructed using DNA, whose outputs are used as inputs for other Fredkin gates. Thus, it can be concluded that arbitrary circuits of Fredkin gates can be constructed using DNA. This paper provides the initial threshold to building of more complex system having reversible sequential circuits and which can execute more complicated operations. The novelty of the paper is the reversible designs of sequential circuits using Fredkin gate. Since, Fredkin gate has already been realized using DNA, it is expected that this work will initiate the building of complex systems using DNA. The reversible circuits designed here are highly optimized in terms of number of gates and garbage outputs. The modularization approach that is synthesizing small circuits and thereafter using them to construct bigger circuits is used for designing the optimal reversible sequential circuits.

Polymer materials offer unique properties for fabrication of micro-optical systems. The ability to engineer the optical and mechanical properties of polymers, the low cost of polymers, and the wide choice of fabrication methods make polymers particularly attractive for low cost, and potential mass production of micro-optical elements and integrated micro-optical systems. An overview of the current state of the art in polymer micro-optic fabrication technology and applications to optical MEMS is presented.

The physical principles underlying a three-dimensional (3D) laser microstructuring technique are outlined, its applications for the fabrication of 3D (nano)micro-structured materials are presented. The direct laser writing and holographic recording in SU-8 photoresist are described. The limits of the lateral and axial light localization of a Gaussian pulse/beam at the focus are derived for the multi-photon absorption taking into account the threshold of photomodification. Prospective holographic patterns formed by interference of circularly and linearly polarized beams are discussed.

Coupled modes of surface plasmon polariton in two metal/dielectric interfaces are studied experimentally by using attenuated total reflection (ATR) method. Metal/dielectric interfaces are fabricated as metal gap waveguides on a high refractive index prism. ATR spectra are analyzed by mode analysis for the metal gap waveguide. A tapered metal gap waveguide is proposed as an effcient coupler from optical fibers to nano-optical circuits. FDTD simulations show adiabatic conversion of wavenumber of coupled surface plasmon polariton.

Flat panel displays (FPDs) such as liquid crystal or plasma displays require defect free and highly planer substrate panels in its manufacturing processes. Therefore, it is necessary to remove and analyze a killer dust particle on the panel surface in order to improve a problem and feedback to manufacturing process. However, nanometer-sized dust detection is difficult with an optical microscope and polarized light analysis method because of diffraction limit of light wave. Moreover, a detection method with an electron microscope has a problem, because a detection area is limited. This paper describes a large area detection of nanometer-sized dust on the surface of substrate using an evanescent wave illumination. Samples used in the experiment are polystyrene latex beads with diameter of 10μm, 1μm, and 200nm. A CCD camera observed a light scattering from polystyrene latex beads. The position of polystyrene latex bead could be specified from the scattering light image. This result shows that this method is effective for nanometer-sized dust detection in a large area.

We propose an optically controllable device Photorefractive Connection Module (PRCM) for free-space optical interconnection between boards. The optical signal composed of a large number of spatially divided channels passes through the photorefractive material which is core of PRCM. In the photorefractive material, diffraction gratings are induced only where the control beam and the pump beam are illuminated. The signal beams in desired spatial channels can be diffracted by setting an appropriate pattern of the control beam and extracted by separating from the control beam with a beam splitter. In this study, we use organic photorefractive polymer PATPD as the photorefractive material. Diffraction efficiency of PATPD is comparable with thick inorganic crystals although the thickness of PATPD is less than 1/10 of these crystals. Thin gratings have a large advantage for PRCM because the thickness of the gratings causes large crosstalk between spatial channels. In addition, the constraint of phase matching is reduced because the phase mismatch is proportional to the thickness of the material. The decrease of the phase mismatch provides large allowance for misalignment of incident angle of beams; therefore it becomes easy to adjust incident angles. We reveal the relation of diffraction efficiency to angular difference of PATPD by analysis and experiment. Diffraction efficiency decreases by half at the difference of 0.5^o, which is about ten times larger than that of thick crystals. We demonstrate that it is possible to extract the signal beams in desired channels and reconfigure the extraction pattern according to optical control by using PATPD.

In the micro-machining process for fabricating optical devices, the fast atomic-beam etching (FABE) or the ion-beam etching (IBE) is used. However, the etch rates of these processes are typically around a few tens nm/min, so the higher etch-rate is strongly required to reduce the processing time. We investigated an etching process of a silicon-dioxide (SiO₂) using an electron-beam-excited plasma (EBEP) to realize a novel micro-machining process without any bias-power supply. The EBEP has an excellent potential for applying self-bias to the non-planar thick dielectric materials with the high-density electron beam. In the direct current (DC)-EBEP, the non-uniformity of etching and the thermal damage to photo-resist were observed. To overcome these problems, we have developed a pulse-modulated EBEP, and thus the non-uniformity of etching and the thermal damage were improved. Moreover, the maximum etch-rate of 450 nm/min was obtained and an anisotropy etching was realized. An optical fiber as a non-planar material was etched to demonstrate the application of this process. The clad area was etched for fabricating a core lens. We have found that the pulse-time-modulated EBEP has an excellent potential to realize micro-fabrications of optical fibers with the etch rate several times higher than that of the conventional FABE and IBE processes.

In this paper, we propose a selective erasure method for multiplexed holograms in a photorefractive crystal using a phase conjugate mirror (PCM). In this method, for the accurate selective erasure, we use pai phase shift between the relative phase of the diffracted beam to the transmitted beam by the hologram in photorefractive crystal and the relative phase of the object beam to reference beam in recording process by setting the direction of c-axis to the appropriate direction. In the selective erasure process, the diffracted beam and the transmitted beam by the original hologram in main memory are returned to main memory by PCM. These returned beams automatically propagate through the strictly same pass as the diffracted beam and the transmitted beam. Furthermore, by these returned beams, the pi-phase shifted hologram is overwritten on the original hologram by setting c-axis of main memory to the appropriate direction. Therefore, the pi-phase shifted hologram is automatically overwritten on the strictly same position as the original hologram without the high precise alignment and the original hologram is selectively erased. We perform the analysis and the experiment on selective erasure and demonstrate that one of the multiplexed holograms is selectively erased with our method.

The biological flow characteristics inside a rugged surface type microchannel are investigated experimentally using a micro-particle image velocimetry (micro-PIV) method. The main objectives of this study are to understand the blood flow structure inside a micro-domain blood vessel and to identify the feasibility of nano-scale fluorescent particles for velocity field measurement in a micron-sized channel. The flow field is analyzed with a spatial resolution of 1K×1K pixels at low Reynolds number flow. To obtain the spatial distributions of mean velocity, 100 instantaneous velocity fields are captured and ensemble-averaged. As a result, for the case of blood flow, there are substantial cell deformation and variations to pass through the rugged surface of a microchannel and the clear velocity vector field was acquired by using the present micro-PIV technique.

We report small reflecting mirrors with high reflectance, which are fabricated by using square quartz chips. These quartz mirrors are going to be used in the construction of a miniaturized Fabry Perot Interferometer (FPI) with a commercial ring type PZT from Fuji Ceramic Company. The dimension of quartz substrates is 10×10mm with a thickness of 1mm. The high reflectance of mirrors is obtained by depositing multi-layer thin films on quartz substrates. Magnetron RF sputtering machine is used to ensure that the thickness of dielectric coatings can be precisely controlled. These mirrors are measured by SEM and AFM and the reflectance is detected by a visible light spectrometer. The maximum reflectance of these mirrors is about 99.4% on the designed wavelength 553nm. A small FPI set up by this kind of mirror can have a theoretical finesse of 522, and if a PZT resonator with a length of 7.22mm is used, the resolution of this small interferometer can reach 4.06×10^-5nm, in another word, the resolving power is 1.36×10⁷.

In recent years, reversible logic has emerged as a promising computing paradigm having its applications in low power computing, quantum computing, nanotechnology, optical computing and DNA computing. The classical set of gates such as AND, OR, and EXOR are not reversible. Recently, it was shown how to encode information in DNA and use DNA amplification to implement Fredkin gates. Furthermore, in the past Fredkin gates have been constructed using DNA, whose outputs are used as inputs for other Fredkin gates. Thus, it can be concluded that arbitrary circuits of Fredkin gates can be constructed using DNA. This has been the driving force leading to the design of reversible adder and multipliers using Fredkin gate. The ripple carry and carry skip adders designed from Fredkin gates already exist in literature; the present work provides an comprehensive extension and novelty to the existing work by introducing the reversible carry look-ahead adder and reversible multipliers using Fredkin gate. The reversible multipliers designed using Fredkin gates are array multiplier, Baugh Wooley multiplier and Wallace tree multiplier. Since, reversible 4:2 compressors are required for the design of reversible Wallace tree multiplier; hence 4:2 compressor is also designed with Fredkin gates. The reversible circuits designed and proposed in this paper form the basis of the ALU of a primitive DNA CPU.

We determined the annealing dynamics of As_Ga antisite defects in As ion-implanted GaAs based on a model where As_Ga antisite defects trap photo-excited carriers. An Arrhenius plot of the carrier decay rate vs. annealing temperature in the high temperature regime gave an energy E_PA, which was different from true activation energy. The annealing time dependence of E_PA obtained by the two diffusion models (self diffusion and V_Ga vacancy assisted diffusion of defects) were compared with E_PA's obtained form already published works, which proved that the density of V_Ga vacancy was high enough to assist the diffusion of As_Ga antisite defects and that the annealing dynamics of As_Ga antisite defects was V_Ga vacancy assisted diffusion.

This paper describes the low-temperature bonding of a lithium niobate (LiNbO3) waveguide chip to a silicon (Si) substrate for integrated optical systems. The bonding was achieved by introducing the surface activation by plasma irradiation into the flip-chip bonding process. After the surfaces of the Au thin films (thickness: 100 nm) of the LiNbO3 chip and the Si substrate were cleaned using an Ar radio frequency (RF) plasma, Au-Au bonding was carried out only by contact in ambient air with applied static pressure. The bonded chips fractured at bonding temperature higher than 150°C because of the coefficient of thermal expansion (CTE) mismatch. The LiNbO₃ chips were successfully bonded to the Si substrates at relatively low temperature (100°C). The die-shear strength of the LiNbO₃ chip was estimated to be more than 12 kg (3.8 MPa), the upper limit of our shear testing equipment.

The orientation control of liquid crystal (LC) molecular on the polyimide film has been necessary to fabricate LC devices. Nano-rubbing by atomic force microscope (AFM) has been proposed as the one of methods to control it precisely. In the method, a thin polyimide film was rubbed by a sharpened AFM probe-tip with relatively strong load force. However, the method has some drawbacks; the frictional wear of AFM probe-tip and the difficulty of reorientation after rubbing. In this paper, we have proposed the orientation control of LC on the polyimide film and using direct AFM nano-rubbing method with weak load forces. The change of LC alignment was quantitatively observed by a polarization microscope and birefringence-contrast scanning near-field optical microscope. The effect of scanning density was strong for azimuth angle but the effect of the scanning velocity was weak for both retardation and azimuth angle. An optical switching device was developed utilized isotropic-nematic phase change of liquid crystal which was rubbed in the grating pattern with methyl red dying, and the optical device was operated at the frequency of 0.5Hz. As a result, The proposed method had an effective method to fabricate novel liquid crystal optical devices.

We report on the rough methods for transforming of external quantum efficiency and power efficiency of organic light-emitting devices (OLEDs). The calculation system based on supposing a perfectly diffuse electroluminescent lambertian surface can be useful for appraising external quantum efficiency and power efficiency in research work. And we set up model of transform for external quantum efficiency and power efficiency of OLEDs and develop computer program to simulate scaling modulus.

The multi-modal miniature microscope (4M) device for early cancer detection is based on micro-optical table (MOT) platform which accommodates on a chip: optical, micro-mechanical, and electronic components. The MOT is a zeroalignment optical-system concept developed for a wide variety of opto-mechanical instruments. In practical terms this concept translates into assembly errors that are smaller than the tolerances on the performance of the optical system. This paper discusses all major system elements: optical system, custom high speed CMOS detector and comb drive actuator. It also points to mutual relations between different technologies. The hybrid sol-gel lenses, their fabrication and assembling techniques, optical system parameters, and various operation modes are also discussed. A particularly interesting mode is a structured illumination technique that delivers confocal-imaging capabilities and may be used for optical sectioning. Structured illumination is produced with LIGA fabricated actuator scanning in resonance and reconstructed using sine approximation algorithm.