Production of a fine pattern is necessary to get a high integration degree of integrated circuits. The conventional methods which utilize high numerical aperture and short wavelength exposure are limited by designing and manufacturing of a practical lens and make the focus depth narrow. Resolution enhancement techniques (RETs) have, therefore, been required and proposed. This paper introduces a phase-shifting mask, a typical RET, points out the problems and inconsistencies of conventional optical imaging theory and explains the image formation concept of expansion of plane waves. Essentially using this concept, an attempt is also made to describe some other typical RETs with potential.

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Kinoform synthesis by an electro-optic hybrid system using an interpolation method is proposed. A programmable liquid crystal spatial light modulator is used as a kinoform. The phase distribution of the kinoform is optimized using the simulated annealing. The cost function is represented by the mean square error between a desired image stored in a computer and a reconstructed image detected by a charge coupled device camera. The interpolation method enables one to reduce the random noise effect in the reconstructed image. Some experimental results are presented.

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A blind deconvolution method using the concept of subband filter banks has been proposed. This method makes possible the speedy convergence of solution, due to estimation of supports of the reconstructed images by a deconvolution in the lower layer. We apply the method to blind deconvolution by a simulated annealing algorithm and confirm its usefulness.

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We made a parallel aligned liquid crystal spatial light modulator (PAL-SLM) respond within 6 ms to meet requirements for a single-SLM color projection system. This was done by adjusting thicknesses of its optical addressing layer and its light modulating layer.

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A numerical model based on ray optics formulation taking the optical path length into account was described and applied to numerical investigations on a thermal birefringence compensation scheme proposed and experimentally demonstrated by Q. Lü et al. [Opt. Quantum Electron. 28 (1996) 57]. Taking into consideration the thermal lensing effects of laser rods depolarization losses and spatial intensity profiles of depolarized beams were calculated for the scheme. It was theoretically confirmed that using a polarization rotator and imaging optics effective compensation for the birefringence in rods is possible for a wide range of pumping power.

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Spectrally pure high-power tunable single-mode operation of a pulsed Ti³⁺:sapphire laser by a tunable injection-seeding is reported. The injection laser was a cw diode laser pumped, spectrally narrowed tunable Cr³⁺:LiSrAlF₆ (Cr³⁺:LiSAF) laser with a grating in the auxiliary cavity. Single-mode tunable operation of a pulsed Ti³⁺:sapphire ring oscillator was obtained at different wavelengths in the range between 818 nm and 848 nm with a typical linewidth of 0.006 cm^-1. To extend the applicability of this operation to a differential absorption lidar system, the single-mode Ti³⁺:sapphire oscillator output was amplified and a high energy output of 38 mJ was obtained with the same linewidth.

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A frequency-shifted feedback (FSF) laser has multi frequency components with simultaneous linear chirping in its oscillation spectrum even though the gain medium is homogeneously broadened. The spectral intensity and its bandwidth were analyzed by the proposed spectral dynamics model based on the regenerative amplification of the continuously chirped comb components with phase shift according to each round trip in the cavity. The spectral intensity peaks at an instantaneous frequency which depends on the net gain in the cavity and the gain bandwidth of atomic transition. The oscillation bandwidth is defined as the product of the saturation-broadened bandwidth and the total resonant modes contributing to the FSF operation.

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We showed theoretically that coordinate transformation is effective in laser cavities because self-reproducible and coordinate-transformed complex amplitude pairs can exist in a laser cavity. Therefore, the intensity profiles in laser cavities can be designed within the limitations of the compatibility conditions.

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We measured the third-order optical nonlinearity of regioregular head-to-tail coupled poly (3-hexylthiophene) (HT-PHT) and regiorandom poly (3-hexylthiophene) (R-PHT) around exciton resonance using degenerate four wave mixing. The observed value of |χ⁽³⁾| at the exciton resonance peak of HT-PHT is in the order of 10^-9 esu which is approximately three-fold larger than that of R-PHT. We observed for the first time the enhancement in optical nonlinearity that occurs through the control of regularity of the polymeric structure. Response time of the nonlinearity was also measured using the transient grating method. The decay time of the transient grating in R-PHT and HT-PHT was less than 2 ps.

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An acute retroreflector having dihedral angles of 45, 60 and 90 deg exactly reflects incident rays in the opposite direction. Beam pattern or wave front of the reflected light of the acute retroreflector can be controlled by tuning dihedral angles. We present here a new method for calculating the reflected wave front of the acute retroreflector, in which the wave front is calculated with high accuracy and in a shorter calculation time than by the conventional ray trace method.

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Calculations have been done for the modulation transfer function of a superresolution optical disk with a combination of optical path filtering and saturable absorption techniques. The results reveal that optical path filtering alone can only equalize, to a certain degree, the spatial frequency response of the optical disk system, but it can not attain any response beyond the cutoff frequency. With an additional saturable absorption layer in-between the substrate and the information layer, it is found that the optical response both under and beyond the cutoff frequency can be greatly improved.

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We present the architecture of novel optoelectronic parallel computing called optical array logic network computing (OAL-NC). In the OAL-NC, electronic processing elements execute local operations, whereas an optical network processor is dedicated to global operations as well as data transfer. As a prototype of the OAL-NC, a 166 pixel system is designed at a logical level. Issues associated with the design task are discussed.

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Imaging characteristics for holographic objective lenses application to optical disk pick-ups was analyzed by a comparison between flat and spherical aplanatic hologram lenses with the aid of the third order aberration theory and ray tracing method. The aplanatic hologram lens image field was 0.5 deg for NA=0.5 with focal length f=5 mm under the Marechal criterion. The results indicates that the aplanatic hologram lenses are feasible for optical disk applications.

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Penumbral imaging is a technique for imaging of neutrons or other penetrating radiations. The technique uses the fact that spatial information can be recovered from the shadow or penumbra that an unknown source casts of a simple large circular aperture. The limitation is that the straightforward image reconstruction will introduce some significant distortion for a large field of view because of non-isoplanaticity of the aperture point spread function. In this paper, a genetic algorithm (GA) is proposed for reconstruction of penumbral images and the technique allows distortion-free reconstruction over a large field of view. Furthermore, because in GA the complicated a priori constraints can be easily incorporated by appropriate modification of the cost function, the algorithm is also very tolerant of the noise.

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We have succeeded in video rate analysis of fringes stabilized by an active interferometer placed outside optical benches. The interferometer uses the closed loop control of injection current of a laser diode to compensate for fringe movement that is detected by a spatial filtering detector. A video image of the locked fringes with tilt is supplied to the real-time fringe analyzer that delivers unwrapped phase distribution from the three phase shifted fringes generated by the electronic moiré method. For a concave mirror of 130 mm diameter placed on a wooden desk we observed the repeatability of λ/60 for P-V surface error of λ/5.

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A new imaging system based on optical frequency domain reflectometry is presented. The intensity-integration effect of the charge coupled device camera to be used acts effectively as a low pass filter for the intensity fluctuation and the 2nd order moment of the detected signals is proportional to a low beat frequency component of the interference signal. Consequently, two-dimensionally imaging of the reflectance of a selective plane located in scattering media is demonstrated.

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HBDD:Recently developed scanning near-field optical microscopy has drawn attention to the problem of describing the electromagnetic field in the close vicinity of a surface. In this work, we present a numerical simulation that solves rigorously the field equations for a dielectric-air-dielectric layer system with arbitrary one-dimensional structure at its interfaces. Our theory is applied to calculate the intensity of the near field transmitted at the center of the tip of a probe as it is moved at a constant height above a surface with two identical topographic defects. The effects on the optical image due to the separation of the objects, and the shape difference between the ridges and grooves are discussed. The resolution limit and the conditions for near field interaction are determined.

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We have developed a novel sample-tip regulation for a near-field optical microscope: an ultrasonic resonance regulation method. The regulation range is from 0 to 50 nm. It shows not only stability, simplicity in construction, but also versatility in vacuum, magnetic field, and low temperature environments. The main advantage of this technique is that it is a non-optical detecting scheme, which is very important for near-field spectroscopy. Such construction can also be used as a force microscope to study the topography of insulating samples. The laser light induced force interaction in the near-field range has been observed for the first time, showing that aided by laser radiation, the shear force between sample and tip can be changed depending on the type of sample. This can be interpreted as the light induced optical tip-sample interaction of light pressure effect. The van der Waals dispersion energy and the optical binding energy induced by laser beam between dielectric tip and samples play important role. The effect confirms a theoretical prediction. This new technique and phenomenon will add new aspects to near-field optics.

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The vertical column abundance of NO₂ is measured using direct sunlight. The solar spectra in the wavelength region of 430-450 nm observed from the earth's surface are ratioed with a reference spectrum taken from the Kitt Peak Solar Flux Atlas. The large Fraunhofer features (20-40%) are eliminated by wavelength correction, resolution matching and ratioing of observed spectra to the reference. The retrieved values of the NO₂ vertical column density are in a range of (2-15)×10¹⁶ molecules/cm² with an accuracy of better than 3%. This result demonstrates the usefulness of the Kitt Peak Atlas in the study of tropospheric NO₂ concentration, giving a standard extraterrestrial solar spectrum for the case in which the Langley method is not readily applicable.

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In Raman-Nath diffraction by water, the intensities of even order light beams are selectively enhanced by suspension of microparticles. The diffracted beams remain for several seconds even after the ultrasonic oscillation stops. These phenomena are elucidated by assuming the laminar arrangement of micropaticles due to the ultrasonic wave.

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