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In this paper, we have proposed a new type of DIRIM with suspended membrane resistor (SMR) structure, while mainly focusing on its implementation technology which includes selection of resistance material and fabrication technique of the membrane; design of Read-In-Integrated-Circuit; and implementation of silica-base MEMS process. Some performance parameters of the device are quoted to conclude the advantages of this new type of DIRIM and make an outlook on the key development in the future.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Air-guiding photonic bandgag (PBG) fibers are new kind fibers which are quite different from conventional correspondence ones. In this paper, we studied the light transmission properties and light wave modes of hexagonal air-guiding PBG fibers. The fiber core is 10μm diameter air hole, surrounded by a cladding of 71.5μm diameter. The outer-cladding of the fiber is about 185μm. The experimental results show that when the wavelength ranges from 1430 to 1600 nm, there is merely no attenuation. It means that in these new fibers, light wavelength ranges widely. In addition, light wave mode and fiber core are the same in symmetrical structure. The theoretical results coincide with experimental results exactly.

Microstructure fiber is a new kind of optical fiber. An arrangement of air holes running along the full length of the fiber provides the confinement and guidance of light. The light is confined in the silica core along the fiber axis. This fiber has endlessly single mode, special dispersion characteristics and so on. Using a vectorial effective-index numerical method, we investigated the dispersion characteristics of a microstructure fiber with honeycomb cladding structures. The dispersion, dispersion slope, and Kappa parameter can be designed neatly by changing the air hole size and the separation of the holes in fiber cladding. We demonstrated the Microstructure fiber with large absolute value of normal dispersion and negative dispersion slope at the wavelength of 1550nm. Conventional communication non-shifted single-mode fibers and nonzero-dispersion shifted fibers (NZ-DSF) can be compensated efficiently using the microstructure fiber at the wavelength around 1550nm.

Mach-Zehnder interferometer (MZI) 2×2 thermo-optic switches, based on parabolically taped MMI couplers, have been designed in this paper. The theory of the parabolically tapered MMI coupler is studied to estimate the optimal length, and then the effective index method (EIM) and the beam propagation method (BMP) are utilized to simulate these devices to find out the optimal length. The values of waveguide parameters are set as: the refractive index difference is chosen to be 0.75%, the width of the MMI field is 30 micron, the distance between the MZI arms is 100 micron and the separation between the access (input/output) waveguides is 250 micron. The simulated results show that the performances of the tapered coupler is better, whose the second width is equal to 25 micron. MMI coupler is also simulated by BPM. Although the tapered coupler can not offer performances as well as those of other MMI coupler, it can offer compact devices. The switches, based on conventional MMI couplers and tapered couplers, are simulated at the same of access waveguide separation and MMI width. Simulated results show that although the performances of this new structure are not as good as those of the switches based on conventional MMI couplers, but can reduce the length of the device effectively. This compact characteristic is important for integrated planar optical circuit.

The purpose of this paper is to present a grating-assisted nonlinear limiting method based on the principle of index mismatching and grating diffraction. In addition, various nonlinear organic materials have been tested in the optical limiting system. A few examples with experimental results are presented. Using a YAG nanosecond pulse laser at 532 nm as a simulated threat laser source, we tested the optical limiting characteristics of the methyl-red doped nematic liquid crystal films. In the meantime, we observed some quite interesting optical phenomena, such as self-defocusing diffraction rings, dark spots in the far-field behind the cell. Our experimental results presented in the paper show that the methyl-red doped nematic liquid crystal films posses a good optical limiting performance. When the input energy focused on the cell increases from approximately zero micro Joule to approximately 200 micro Joule, the output energy on the far-field exit plane is kept under 1 micro Joule. We will describe a completed optical limiting system with Q-switched frequency-doubled 12- ns Nd:YAG laser, dual-channel detectors, and computer processing units based on Lab-view software and its design considerations.

not available.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical nonlinearity and multiplex holographic storage using azo side-chain polymer are studied by using degenerate four- wave mixing and polarized pump-probe laser method. The He-Ne excitation laser wavelength is located at the tail end of the absorption peak of the sample. This material shows high grating diffraction efficiency and promises information storage capability using weak absorption. The diffraction efficiency of the grating is up to the order of 10 -2 . The effect of input beam polarization planes on grating is studied. The diffraction grating efficiency is lowest when the polarization of the redout beam is orthogonal to that of both writing beams. An angle multiplex holographic storage study is also performed in the sample. Information can be stored for a long time at room temperature. The information readout of this multiplex holographic storage system can be controlled by the polarization state of the readout beam. Dependence of grating diffraction efficiency on the sample temperature is studied. It is demonstrated that the higher the temperature under the melting temperature of the sample, the higher the diffraction efficiency and the faster the relaxation time of the grating. The grating is completely erased by increasing the temperature over the melting temperature of the sample. Reading the grating with a circularly polarized light does not erase the grating. When two recording beams are turned off, a large part of the grating remains for a long time and only a small part of the grating degrades. The results show that the azo side-chain polymer is a good information storage material. The anisotropic optical nonlinear refractive index of the sample is also measured. The relationship of the nonlinear refractive index of the samples, the different ratios of azo functional groups in the polymers, and the temperature of the sample are also studied. The highest nonlinear refractive index is up to the order of 10 -2 . The optical nonlinearity of the samples increase with increasing sample temperature. No anisotropic nonlinearity appears when the temperature of the sample is over the melting temperature of the sample. The anisotropic nonlinearity levels of three samples with different azo side-group ratios in the polymer are compared.

Third-order nonlinearity and polarization holographic storage in acceptor-donor azo dye-doped PMMA films arestudied by using nonresonant degenerate four-wave mixing with a He-Ne laser. The samples exhibit reasonably large third-order susceptibility and strong polarization sensitivity, and the highest third-order nonlinear susceptibility is up to the orderof 1 O esu. The relationship between optical nonlinearity and "push" and "pull" electron ability in polar azo molecules isstudied, and further effect from a push-electron group attached to azobenzene ring on third-order nonlinearity of thesamples is explored. Third-order nonlinearity of the sample is found to be proportional to the push-pull electron ability of polar azo molecules. Attaching a side group with push-electron ability to the azobenzene ring increases third-order nonlinearity (dipole moment) of the material. Polarization holographic storage properties in azo dye-doped PMMA filmsare also studied. The samples show strong polarizzition sensitivity and real-time information storage properties. Thepolarization hologram in the sample results from a birefringent grating formed by photoinduced reorientation of polar azomolecules. The optical phase conjugation signal consists of both fast and slow parts when two recording beams are turnedoff. They respond to the processes of four-wave mixing and holographic grating. It is demonstrated that nonresonantnonlinearity of samples mainly results from photoinduced anisotropy of polar azo chromophores. The advantages ofnonresonant nonlinearity and its applications are discussed.KEYWORDS: acceptor-donor azo dyes, third-order nonlinearity, holographic storage, birefringence

We propose a set of novel optical limiters by sandwiching index-matched nonlinear liquid between a glass plate and a relief grating. Strong light beams can change the index of the liquid to induce index mismatch and reactivate grating to diffract, reflect or evanesce most of the output light away to protect eyes or sensor. In this paper, different gratings for the use of optical limiting including diffraction gratings, total-reflection gratings and sub- wavelength gratings are analyzed and compared.

The intensity-dependent nonlinear refraction in a non- resonant five-level molecular systems is studied in detail using rate equations, including saturable refraction, reverse saturable refraction, and the transition between these two effects.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Four-wave mixing spectroscopy is presented as a convenient and effective optical method for the study of excited-state optical storage properties and nonlinear mechanisms in a dye-doped polymer film. The dynamic processes of optical storage properties and the efficiency of the diffraction grating are discussed. Backward-scattering four-wave mixing and forward-scattering four-wave mixing optical configurations are presented. A simple energy-level model is used to explain the excited-state optical storage mechanism, resulting from photo-induced excited-state population grating and trans-cis isomer grating.

The optical limiting of Q-switched Nd:YAG radiation oat 532 nm is performed using Fullerenes-toluene solution contained in a cell with a random rough surface. One of the inside surface of K9 glass was roughened. At low incident fluences the random rough surface windows index matches with fullerenes solution, so optical limiting behavior in fullerenes-toluene solution is based on excited state absorption. At high incident fluences thermally induced index change causes a sufficient index mismatch at the random rough surface and leads to significant scattering. Additional limiting due to scattering occurs. The limiter of excited state absorption/random surface scattering is superior to the limiter of purely excited state absorption.

Optical power limiting of Fullerenes/PMMA has been studied based on a time-resolved single-beam technique. A nanosecond/picosecond Nd:YAG laser system with pulse width of 8-ns, repetition frequency of 10 Hz and wavelength of 532-nm was employed. Temporal profile of pulse beam is Gaussian profile. When the peak power density of incident laser pulse Pin is 180 WM/cm2, the incident and the transmitted laser pulses versus time are measured using a 4402 Boxcar of 0.4 ns time resolution. The experimental results have shown that, at high irradiance the transient transmitted power density increases nonlinearly and limits to less than 30 MW/cm2. In our experiment, the switching speed of the optical power limiter is less than 5 ns. The measured results can be fitted on the excited state absorption theory. Theoretical results are shown that the excited state absorption saturation occurred at higher peak power.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

As a kind of nonlinear optical materials, polydiacetylenes (PDAs) have attracted great attention because of their large third-order susceptibilities, ultrafast responsibilities, and high damage threshold, etc. 5-(2-methylthio-4-methyl)- pyrimidinyl-2,4-pentadiyne-1-ol (PDAA) and its derivatives were synthesized. The optical limiting characteristics of these compounds were demonstrated with nanosecond and picosecond pulses at 532 nm. With linear transmittance as high as 87%, the limiting threshold and limited amplitude of PDATS(PDAA tosylate) were observed to be 200 mJ/cm2 and 150 mJ/cm2 respectively, which are lower than that of C60 with the same high transmittance for visible light. A five-level model describing reverse saturable absorption (RSA) of PDATS was proposed to explain its optical limiting effect. The excited-state absorption cross section and the excited-state lifetime were estimated to be 4.0 multiplied by 10-19 cm2 and 0.6 microseconds respectively.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report experimental results of the nonresonant third-order nonlinear properties of an acceptor-donor azo dye doped in polymethyl methacrylate (PMMA) thin films by degenerate four-wave mixing with a He-Ne laser, which have appreciable nonresonant third-order nonlinearity, (chi) (3) being approximately 4 X 10-4 esu. The OPC signal has strong sensitivity with the polarization of the three incident beams, and the self- refracted phase conjugation by the coupled two counter-propagation beams was studied. In conclusion, nonresonant third-order nonlinear mechanism is demonstrated to be a result of photoinduced birefringence of the azo molecules. The real-time polarization storage properties of the azo dye were used in the interferometry to measure the shape variation of the object.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

All-optical switching in C60 has been studied using pump-and-probe method. The switching process is attributed to excited-state absorption of C60 molecules. Simulated results of the switching behaviors are obtained from a five-level model, which agree well with the experimental data.

In the paper , 4—n-butoxy carboyl-methl-urethane was synthesized by the reaction of 5 , 7-dodecadiyn--1 , 1 2-diol-bis-chloro-formate with buthylaminoacetate hydrochloride. High convertion of monomer in solid state into polymerwas obtained by y-irradiation. We fabricated high optical quality waveguiding film and measured the optical limtingeffect of poly-4BCMU in chloride and nonlinear response time of poly-4BCMU. 1. INTRODUCTION The nonlinear optical(NLO) properties of conjugated polywer polydiacetylenes (PADS) are currenly attractinginterest , because of the fairly large third-order electric susceptibity X (3)and ultrafast NLO response timeE12j, Due tothe possible intrest in NLO application, the synthesis and nonlinear optical properties of PDAs have been extensivelystudied. In this paper, we present a novel synthesis method on poly-4BCMU and study on optical limiting using poly-4BCMU and measure its nonlinear optical property. 2. SYNTHESIS AND PROPERTIES We used 5, 7-dodecadiyn- 1

The dynamic behavior of a neural network is demonstrated by its interconnection weighted matrix. In this paper, we present a Feature Enhanced Interpattern Association (FEIPA) neural network model which is sensitive to special features of reference patterns in the reconstruction. We think of the common part of the stored patterns as redundance and discard its contributions in the associating process. It is equal to enhance the role of special features of the reference pattern in the IWM and in the reconstruction procession. Therefore the IWM of FEIPA is well-distributed and the output before threshold is a little more uniform than that of IPA model. A 2D (8 X 8) optical system is constructed using lenslet array as interconnection to realize the FEIPA model. Digital simulation and experiment results are provided.

In this paper we propose a Feature Enhanced Interpattern Associative (FEIPA) optical neural network. The common part of the stored pattern is regarded as redundance and its contribution in the association process is discarded. Therefore, the output before thresholding is more uniform, and it is more easier for the thresholding performance and increase the iteration speed. Furthermore, the optical implementation is much easier because all the elements of one interconnection matrix are non-negative and unipolar. The theoretical description and the experimental results are presented.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper we propose a feature enhanced interpattern associative (FEIPA) optical neural network. The common part of the stored patterns is regarded as redundance and its contribution in the association process is discarded. Therefore, the output before thresholding is more uniform, and hence, it is easier for the thresholding performance and increases the iteration speed. Furthermore, the optical implementation is much easier because all the elements of the interconnection matrix are non-negative and unipolar. The theoretical description and the experimental results are presented.

A high accuracy optical bistable temperature sensor was proposed and proved experimentally by using a fiber-optic Mach-Zehnder interferometer combined with an electro-optic bistable device.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have measured the nonlinear absorption and nonlinear refractive index changes in ZnSe''ZnS multiple quantum wells at low temperature. The largest change of nonlinear refractive index is 0. 012 and corresponding n2 is 7x1Ocm2IW. The nonlinear mechanism are attributed to exciton band broadening and phase space filling of exciton states. With different excitation wavelengths we have demonstrated the dynamic optical bistabilities in ZnSe/ZnS MQWs.

We have demonstrated a novel optical power limiter which can be used to limit an unstable pulse peak power with temporally smoothing in shape for CO2 laser pulses. The peak power of pulses was limited with 1.1% fluctuation for a 30% change of incident pulse peak power and the frequency of subpulse oscillation on a single pulse was over 30 MHz.