We propose a new concept for an optical network unit using planar microlens array for fiber to the home networks. It is expected from this modeling that an optical coupling loss of 2.5 dB, a polarization dependent loss of 0.5 dB and an extinction ratio larger than 50 dB can be achieved. The structure design and its fabrication method are discussed.

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A new scheme of an amplitude modulated harmonically mode-locked Er-doped fiber ring laser is proposed, and the lasing characteristics are experimentally investigated. The transform-limited sech² pulses at the repetition frequency of 1.64 GHz are stably generated. The pulse width and spectral bandwidth are independent of both the amplitude modulated (AM) modulation signal frequency and the AM modulation depth.

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A simple method is described for fabricating high resolution c⁽²⁾ grating in poled polymer waveguide. It is found that the second-order nonlinearity of corona-poled polymer thin film is erased after visible laser (450 nm) irradiation. The mechanism of the erasure of c⁽²⁾ is discussed. High resolution c⁽²⁾ grating structure in several poled polymer waveguides is demonstrated by direct writing with a cw He-Cd laser.

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A new method for the detection of low oxygen concentration is proposed here. The system is based on the principle of enhancement of fluorescence yield of tetraphenylporphine (TPP) dye at l=656 nm when excited by He-Cd laser at l=441 nm in the presence of oxygen. The sensor head was fabricated by cladding the ARTON fiber core with the poly-4-methyl-1-pentene polymer matrix doped with TPP. The experimental results obtained indicate a good enhancement in the fluorescence when the sensor head is exposed to oxygen. The response was found to be linear and stable in the range of (100 ppm-1%) with the resolution of 0.01%. The sensor response was characterized by studying its response for change in temperature and is discussed below.

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The reflectance of a high-reflectance dielectric multilayer coating mirror tuned to a monochromatic laser wavelength was estimated from its transmittance which was measured with 0.4 ppm accuracy. The transmittance was calculated from its theoretical formula including three parameters (refractive indexes of low and high refractive films (n_L, n_H) and a number of layer units composed of a pair of one low and one high refractive film (N)) which were estimated from the incident beam angular dependence curve of the transmittance. This calculated transmittance agreed with that measured as a ratio of the laser beam power before and after the mirror with 6 ppm difference.

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An optical frequency-domain interferometer incorporating a Kters prism is constructed to offer an excellent instrument for making a stable precision-measurement of material absorption and dispersion. The working stability is well retained over a long-term operation of 15 h, but the spectral resolution is limited to the resolving power of the spectrum analyzer used. The absorption and dispersion measurements are demonstrated by use of two samples of a BK-7 glass plate and rhodamine in ethanol.

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This paper deals with the propagation law of mutual intensity and cross-spectral density of the light emitted from an extended broadband spectral source that is spatially incoherent. The mutual intensity of light does not obey the same mathematical formalism as the Van Cittert-Zernike theorem applicable to quasi-monochromatic light, although the cross-spectral density of light does in the propagation zone of the Fresnel diffraction region.

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Coherent optical code division multiplexing is a novel method using the phase of optical pulse as the bipolar code for future fiber-optic communication networks. Some optical bipolar codes with a repetition frequency over 10 GHz are generated experimentally and their fundamental properties are elucidated. The key features of the method, auto- and cross-correlation of these codes, are shown experimentally and compared with the theoretical results. Interference between two optical narrow pulses with high repetition frequency is investigated experimentally under various conditions of optical phase and wavelength as the basis of the method. A guaranty of realization of the technique is shown.

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A new concept is developed for improving the laser intensity distribution in quasi-far field using geometrical optics of a continuous phase (so-called edge-shaped plate). The diffraction fringe on a quasi-far field beam pattern of a well collimated He-Ne laser beam 5 cm in diameter is mitigated by the insertion of an edge-shaped plate with a super-Gaussian (n=40) surface profile. A diffraction code using Fresnel-Kirchhoff diffraction integration was developed to calculate diffraction patterns of aspherical optical elements. The measured beam profile is in good agreement with the calculated beam pattern.

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Effects of humidity on nonlinear transmission properties due to saturable absorption were investigated using eosin-Y-doped polyvinyl alcohol (PVA) films which had been exposed to a highly humid atmosphere. In a pump-probe measurement, a transmitted probe signal changed in every shot of the pump-pulse irradiation, and tended to approach a steady characteristic. Simultaneous measurements of the transmitted probe power and the phosphorescent lifetime showed that these phenomena stem from the phosphorescent lifetime being lengthened by the successive pump irradiations. This increase in lifetime was found to have originated from reduction of a nonradiative decay rate of an excited state of the dyes. The recurrent pump irradiations are believed to remove moisture, which has strengthened the nonradiative decay rate, from the PVA films.

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We consider the optimum incident angles of cross polarized four-wave mixing with a photorefractive crystal. First, the phase matching angles are obtained for two operation modes: one in which the writing beams are ordinary rays and the reading beam is an extraordinary ray, we call this Mode 1. The other in which the writing beams are extraordinary rays and the reading beam is an ordinary ray, Mode 2. Next, practicable ranges of the incident angles are calculated considering of the total internal reflection of the phase conjugate beam in cases where the two writing beams illuminate the same surface of the BaTiO₃ crystal and where they illuminate the neighboring right-angled surfaces, respectively. Then, the coupling coefficient is determined as a function of the incident angle, and the optimum incident angles for effective beam interaction in Mode 1 and Mode 2 are estimated.

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We describe spatial arrangement of polystyrene latex using a microscopic imaging system. A reduced photomask pattern is imaged on the particles in a water-filled cell so that polystyrene spheres align in a two-dimensional pattern. Calculating the forces exerted on the spheres by isolated line pattern, we investigated an optimum size for sphere diameter and the line width of the patterns. We are able to align spheres in real-time by this technique.

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Degree of color constancy was measured when color memory was involved in color comparison judgment. We used the Optical Society of America (OSA) Uniform Color Scales as stimulus color samples, and chose 20 color samples as test stimuli. Four illuminants of 1700, 3000, 6500, and 30,000 K were tested. The observer, completely adapted to a test illuminant, saw a test color sample and stored its color in his memory. After being readapted to the reference white (6500 K), he started selecting a color sample from among the 424 OSA samples which matched the test sample in his memory. We employed a memory matching method called cascade color matching, in which the number of selected color-samples was gradually reduced in four stages. In the final stage, the observer selected a color sample. The results show that, for most test colors, the distributions of selected colors in stages 1 to 4 were similar among all illuminants, and that the u'v' chromaticity distance between a test color under 6500 K and its matched color was quite short. These indicate that good color constancy was retained in memory color comparison.

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Increasing (or decreasing) the convergence angle can shrink (or expand) the perceived size of an object without changing its retinal size. The present report deals with the question of whether such a change in perceived size affects visual acuity. We investigated the effects of perceived size on the legibility of letters, using a telestereoscope which can control the observer's convergence angle while keeping the size of the retinal image constant. We demonstrated that letters do become more legible (illegible) as perceived size expands (shrinks), although their retinal size stays constant. Then, we measured the ‘threshold’ size of the convergence angle, at which letters became legible from illegible, for several retinal sizes (0.1 to 0.2 deg) of letters. The result shows that the threshold decreases as the retinal size of letters decreases, so that the minimum retinal size of legible letters depends on the convergence angle. This implicates contributions from the size perception at higher levels of the visual system to the determination of visual acuity.

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