The possibility of a super-resolution optical memory using a saturable absorption dye mask layer is theoretically discussed. An equation which estimates the transmittance change of the mask layer has been derived. The numerical simulation shows that an efficient super-resolution is performed when the initial optical density of the mask layer is high.

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A waveguide-type optical frequency shifter based on a rotating half-wave plate is proposed. The underlying principle can be used to realize a bit-rate-free and modulation-code-free optical frequency shifter. The waveguide was formed along the direction on a GaAs (1 1 0) substrate by molecular beam epitaxy (MBE) and reactive ion beam etching (RIBE). A 10-MHz optical frequency shift with 16 V_p-p applied voltage and 22.5% shift efficiency is demonstrated.

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We show analytically that in the presence of cubic and quintic nonlinearities above a certain critical power, multidimensional optical solitary waves could propagate stably in bulk media. To investigate the stability an analytical expression for the solitary-wave fields with an arbitrary transverse dimension is derived through the combined use of Galerkin's method and self-consistent-field approximation.

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Sol-gel processed poled silica films doped with novel nonlinear organic materials, thiazole azo dye (TA), are prepared in high concentration. Resonance enhanced second-order nonlinear optical coefficient of d₃₃=154 pm/V is obtained from TA doped silica film (40 wt%) for the fundamental wavelength of 1064 nm. The value d₃₃ is unvaried for at least 100 h under a high temperature condition (100°C) without any relaxation. Wave-length dependent second-order nonlinearity is also measured.

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The spatio-temporal Fourier transform is usually applied to determine the velocity of an object from a series of standard light intensity frames. In this paper the technique has been extended to determine the object acceleration. The techniques for velocity and acceleration determination based on the spatio-temporal Fourier transform have been applied to experimental low light level images. Under these conditions, the processing time is reduced so that, in those cases in which it is necessary to quickly obtain the object velocity or acceleration, low light level conditions would be advantageous, using intensity filters if necessary.

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Talbot images constructed in the Fresnel diffraction region due to two-dimensional Gaussian beam arrays with amplitude fluctuation are statistically investigated using a mathematical model based on the propagation law of a Gaussian beam. The average intensity distribution of Talbot images is analyzed theoretically, and the corresponding simulation is conducted by computer. The relative fluctuation of the peak intensity to the mean with respect to Talbot images is found to be less than that of the source by approximately 1/4. Furthermore, the effect of the finite size of source arrays on the formation of Talbot images is revealed throughout the simulation as well as the effect of the amplitude fluctuation.

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With the aid of the time-dependent principle of invariance in a semi-infinite homogeneous atmosphere which scatters radiation anisotropically, an expression of the exact solution to the equation of time-dependent radiative transfer for the diffuse reflection function is obtained in terms of an infinite series, which corresponds to a process of multiple scattering. A statistical interpretation of the exact solution is made by the statistical meaning of the corresponding stationary solution.

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We propose here a new optical modified signed-digit (MSD) adder module based on bit plane pattern encoding of MSD digits and pattern operations. The pattern operations required in the algorithm are duplication, combination and shifting. They are simply performed by using optical components such as beam splitters, mirrors and parallel plates, instead of optical logic arrays. An optical MSD adder module comprised of six properly interacting blocks with all optical components packaged on a common substrate is presented in detail. We analyze the system errors caused by manufacture and alignment of optical components, the information throughput, the intensity nonuniformity and the system volume of the adder module.

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We present the concept of integrated processing to combine intuitive processing of neural networks with logical processing of the conventional digital computer. We investigate a way to embody the concept in the neural network system by introducing external constraints in terms of external input. The effect of the external input is analyzed using the generalized projection method. The concept of integrated processing is applied to an image associative memory system, and the system is optically implemented for high-speed parallel processing incorporating it with the computer. The experimental result is presented to illustrate the effectiveness of the external input to control the output of the image associative memory.

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Making use of the idea of synthetic discriminant functions (SDF), a simple way to synthesize a shift, rotation and limited size correlation filter is proposed. The SDF is synthesized by superimposing four 2nd order circular harmonics of a training reference pattern in 4 different sizes. Computer simulation experiments have shown that the filter is indeed shift, full rotation and limited size invariant over a size range from 1 to 1.82. The invariant range can be increased if more training patterns are used.

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Effects of small signal injection on an electro-optical bistable system with a very large delay are theoretically and experimentally investigated from the viewpoint of linear stability analysis. The resonance phenomena and frequency locking are observed when sinusoidal and rectangular small signals are additively injected into the system. Experiments confirm that theoretical results obtained by linear stability analysis are good predictions of the effects of both resonance and frequency-locking phenomena and show the dependence of these phenomena on the system parameters. As an application of the frequency locking phenomenon to the dynamical memory, the phase identification of the memory oscillation using the frame pulse externally injected is successfully executed.

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We have redetermined the absolute values of the nonlinear optical coefficient, d₃₁, of LiNbO₃ by parametric fluorescence and, for the first time, by difference frequency generation measurements to resolve the considerable discrepancy that existed between the values determined by second-harmonic generation (SHG) and parametric fluorescence. We obtain d₃₁=4.8.5 and 4.3.5 pm/V at the pump wavelengths of 488 and 532 nm, respectively, in reasonable agreement with the SHG data. It appears that the previous parametric fluorescence value, d₃₁=5.8 pm/V, was overestimated.

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We analyze the influence of error in the measurement of shear value, which is a major source of error in tested results by the lateral shearing interferometer. A novel method is proposed for accurately measuring the shear of this interferometer. By introducing a defocused wavefront and making use of the wavefront slope data of the defocus and the parameters of the interferometer, we can calculate the shear value precisely, with an error less than the sampling interval of the detector. An experiment was conducted to show the effectiveness of the method.

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An experimental verification of the reflection properties of non-cooperative targets for a time-of-flight laser rangefinder is proposed. Indeed, knowing the light scattering physical properties of usual targets is necessary to determine the optical power budget of such a device. The useful reflection coefficient (RC) is contained at between 0.6 and 0.7 at the wavelength λ (=820 nm), polar diagrams presenting almost a lambertian shape for incident angles lower than 60 The useful RC thus corresponds to the value of the lambertian RC increased by the contribution of the specular RC.

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Absorption coefficient measurements of strongly scattering and weakly absorbing media have been performed using time resolved transmittance of a 100 fs pulse through a 30 mm slab containing latex spheres suspended in water and absorbing ink solutions. The scattering and absorption coefficients were selected so that the optical properties of the media were similar to those of biological tissues. Measured curves of time-resolved transmittance of the pulse through the media were used to estimate the optical properties of the media. The experiment was made at two different wavelengths, 784 nm and 810 nm. Estimated absorption coefficients were in good agreement with those measured in a nonscattering case by a spectrophotometer.

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This paper addresses the important role of how aerosols play in light scattering in the earth's atmosphere and how their characteristics can be retrieved. It is shown here, by referring to typical aerosol types, that more than a half of the atmospheric light is scattered by aerosols, and the aerosol optical properties can be estimated in terms of the scattering behavior. It is also confirmed that aerosol retrieval can be accurately determined by combining polarization and radiance data.

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In this paper we shall present our stochastic model for the transfer of polarized light. We introduce the polarized phase function which is necessary for the exact determination of the scattering distribution for polarized light. Finally, we compare results of variance reduction Monte Carlo simulations based on that model with measurements taken with the DLR-Microlidar. This LIDAR is designed especially for cloud and fog measurements and has two fields of view with two polarization channels each; see W. Krichbaumer et al. (Opt. Laser Technol. 25 (1993) p. 283).

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Atmospheric turbulence sensing by lateral fluctuations of thin beams is described. Practical use of correlation functions of lateral fluctuations to investigate the refractive index spectrum and its parameters, inner and outer scale and structure constant, is presented. A “maximum” method is also shown to derive the inner scale independently of the other parameters, without either knowing much of the turbulence or solving an inverse problem.

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The main features of a Monte Carlo code developed to deal with polarization of lidar returns from water clouds in multiple scattering regime are described. The paper presents an example of results pertaining to a stratified cloud structure, and a series of comparisons of calculation results with measurements carried out in the laboratory. For double scattering a comparison of Monte Carlo results with those of an analytical formula is also given.

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A 50-cm diameter hollow cube-corner retroreflector for a space application was tested with a 60-cm interferometer. To separate the effect of sag due to gravity, the interferograms were taken at six rotational positions, with the retroreflector mounted horizontally. The zero-gravity dihedral angles and the effect of sag were estimated from the interferograms.

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We have numerically analyzed some thermal characteristics of cw long wavelength surface emitting lasers with epitaxially grown semiconductor distributed Bragg reflectors (DBRs). It was shown that the device thermal resistance for GaAs/AlAs DBRs epitaxially fused to GaInAsP/InP emitting layers is 1/3 of that for GaInAsP/InP DBRs and almost comparable to that for the optimum dielectric cavity. The threshold current lower than 10 mA and the electrical resistance lower than 100 Ω are necessary to obtain the cw operation beyond room temperature.

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