Synchronized mode-locking of monolithic mode-locked diode lasers has been demonstrated by injecting the light output from a master monolithic mode-locked diode laser. The master diode laser is a 10 GHz hybridly mode-locked two section InGaAsP quantum well laser. The slave lasers are a 10 GHz two section laser which is similar to the master laser, and a 20 GHz three section colliding pulse mode-locking laser. Both the slave lasers were greatly stabilized at 10 GHz frequency by a synchronous mode-locking mechanism under the injection of master laser pulses.

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Optical solitary waves that propagate in a Kerr medium exhibiting a power-law nonlocal response are studied analytically. The first-principles stability analysis based on quantum field theory shows that within the whole range of the exponent (the fractal dimension) the solitary wave can be stabilized.

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In the recent researches of subwavelength relief gratings, the effective refractive indices are used for calculating the coefficients of reflection and transmission of light waves. The effective refractive indices are given by the effective medium theory for light waves propagating in a bulky stratified medium. This paper describes the ability and limitation of the theory applied to estimate the performance of such subwavelength gratings. The limitation is revealed by numerical calculations using a rigorous electromagnetic grating theory and the effective medium theory. As a result, an understanding of the wave behavior in the subwavelength grating has been acquired, which explains the limitation of the effective medium theory.

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The overwrite cycle characteristics and environmental stability of a phase change optical disk with a new disk structure were demonstrated. The C/N ratio was around 55dB, the erase ratio was around 25dB and the phase jitter was under 50% throughout the one million cycle overwrite test. The accelerated aging test conditions were 90°C, 80%RH, for 600 hours and 70°C, 80%RH for 5,200 hours. The archival and shelf one million overwrite cycle characteristics of phase jitter were stable throughout the aging test. The life expectancy of the disk is anticipated to be more than 60 years in a 32°C, 80%RH environment.

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A novel, parallel aligned optically addressed liquid crystal spatial light modulator has been used to implement an optically writable image memory. The memory uses a two-beam interferometer with optical feedback which exhibits thresholding, hysteresis, and bistability. We discuss the characteristics of the system, and present the results of an experimental demonstration.

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A simple method using a convolution image to locate an object in a scene is described. The image is processed by an optical system using a spatial light modulator in real time. Experimental results are presented with discussion on the improvement in the system performance.

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The object's surface structure can be obtained from an image sequence taken through a conventional CCD endoscope. This paper reports clinical experimental results of the method. The accuracy of the estimation is studied and a method to estimate the reliability of the reconstructed shape is also described.

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It is well known that an inverse problem of biomagnetic imaging is generally ill-posed. Recently several attempts using biocoherence have been reported, but the ill-condition is not considered in these previous methods. If the conventional reconstruction formula is under the ill-condition, the reconstruction problem is also ill-posed and the ill-posedness cannot be improved. In this paper, we propose an approach to estimate the location of current sources under the condition that sources of different positions have little or weak correlation. Our method is based on a well-known regularization method, the truncated SVD method. Compared with the conventional method, our technique allows accurate determination of the location of current sources because it improves the ill-posedness of the inverse problem. We carried out computer simulations using the half-space conducting model and confirmed the effectiveness of our method.

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The improvement of optical gain is an important priority for performance design in most of optoelectronic integrated devices (OEIDs). A two-dimensional simulator is developed for the rigorous analysis and optimum design of devices. With it, we analyze the characteristics of heterojunction phototransistor (HPT) which acts as a light-detector in OEID, and we propose new structures of HPT to increase the conversion gain without much increase in dark current. Then, the simulation of an OEID composed of an HPT integrated over a light-emitting diode (LED) is implemented, and it is shown that the new structures significantly improve the optical amplification for low input light power over the conventional structure.

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We numerically analyzed the thermal characteristic in continuous wave (cw) GaInAsP/InP surface emitting lasers with dielectric multilayer mirrors by using finite element method. From the simulation of temperature distribution in cw devices, we found that MgO/Si multilayer mirror which has a high thermal conductivity is effective for heat sinking; the thermal resistance of device using MgO/Si mirror is nearly half of that using SiO₂/Si one, almost independently of their thicknesses. It was also indicated that the optimum design for other structural parameters, especially the thickness of active region, is important to effectively suppress the temperature increase. The minimum threshold current was estimated to be 3 mA under cw condition for the active region diameter of 4 μm and thickness of 0.5 μm.

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Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (±)2-(α-methylbenzylamino)-5-nitropyridine ((-)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d₃₁=6.8 pm/V, d₃₂=4.7 pm/V,d₃₃=0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (-)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.

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To make holograms from computer graphic (CG) in a short time, a new holographic three dimensional (3D) printer is proposed here. This printer consists of galvanometer scanners, a micro computer and a laser, and uses a holographic contact duplicating method. Experiments have shown that a hologram of 39 41 mm can be obtained in 4 min.

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The absolute longitudinal distance between two points can be determined by the corresponding correlation peaks of two light-waves from a broad-band light source. Using this technique, the height of three-dimensional objects can be measured without 2phase ambiguity. We can also detect the absolute position of scattering seeds in sub-surface or bulk materials such as defects, dislocations or impurities of high purity materials. The wavelet analysis is used to determine the correlation peaks. This technique can be applied to measurement of thickness of a few hundred microns.

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The Fraunhofer diffraction pattern of an aperture formed between a knife edge and a smooth surface of a turned metal cylinder or half cylinder is different from the diffraction pattern of an ideal slit aperture. The diffraction pattern is simulated by adding the light reflected by the cylinder surface to the pattern formed by a slit, and is measured using a cylinder that has been partly cut away so that it can represent either a full or half cylinder. The theoretical and measured patterns agree well with each other.

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In laser triangulation, the determination of the centroid is limited by the image speckle. In this article we present a new method to reduce image speckle. We find the correlation function of image speckle decreases with the change of illumination angle, so for a static object we scan the incident angle within the plane of the light sheet and get a speckle-reduced image, with the time-integration effect of a CCD camera. An analytical description is presented and is experimentally verified.

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We earlier proposed an analytical and prospective method for evaluating projection optical lithography. In this paper, we apply it to more complicated cases, such as optimizing transparency of a half tone phase-shifting mask and considering the resolution enhancement technique which uses both multiple exposure and non-linear resist. We also apply it to the evaluation of isolated line patterns using 1:2 line-and-space patterns.

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A low-speed screen/film system was used to investigate structure mottle, i.e., the density fluctuation of an x-ray film due to inhomogeneous screen structure. The tube voltage dependence of the Wiener spectra of the structure mottle was separately determined for front and back film emulsions. The Wiener spectral values of the structure mottle of the front emulsion were greater than those of the back emulsion at lower tube voltages. The spectral values of the structure mottle of the front emulsion decreased with tube voltage, while those of the back emulsion increased. We explain these phenomena by the behavior of the Wiener spectra of the relative spatial fluctuation of fluorescence intensity due to following reasons: (1) spatial thickness fluctuation of the screen produces a relative spatial fluctuation of x-ray energy absorbed in the screen, and (2) as the distance between the emulsion of the film and the average position of the x-ray absorption in the screen lengthens, the number of random scattering and absorption of light photons increase.

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