We present a fitting method for obtaining a functional form of the refractive index profile of planar microlenses made by ion exchange techniques from total shearing interferometric measurements. Compared to the usual power series expansion fit, this method allows a reduction in the number of coefficients needed to characterize a lens.

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We observed multiple diffraction rings of a cw Ar⁺ laser beam from a nitrobenzene solution of saturable absorber BDN (bis-(4-dimethylaminodithiobenzil)-nickel) caused by the spatial self-phase modulation at low incident optical intensities. We obtained 37 rings for a 200-μm thick sample at an optical intensity of 38 W/mm². The refractive-index change n and effective nonlinear refractive index n₂ were determined from the number of observed rings and by the z-scan technique. We obtained large values of n~0.1 and n₂=-2.9×10^-5 cm²/W. This large nonlinearity is attributed to a thermal effect resulting from linear absorption.

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Unconventional critical relaxations in the dynamics of envelope solitons subjected to a dissipation are predicted in the framework of adiabatic approximation. The degree of “slowness” in the critical relaxation process is controllable either through the loss compensation with gain or through the modulation of the magnitude of nonlinear absorption.

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Reflectance anomalies of random amorphous multilayers are shown to be different dependence on the incident angle for s- and p-polarized light by simulation. Disappearance of these anomalies has especially been observed for p-polarized light propagation at a certain incident angle. It is shown that this incident angle is the extended Brewster angle defined for opaque materials. This phenomenon, i.e., the disappearance of reflectance anomalies, is the Brewster anomaly in random amorphous multilayers made with absorbent materials. Preliminary results of experiments are also presented.

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A novel highly sensitive method to detect the concentration of trace gas for environmental purposes is proposed. This method includes the application of frequency modulation for stabilization of laser frequency, together with optical heterodyne measurement. The shift of resonance frequency of the Fabry-Perot cavity resonator is due to the change of refractive index, accompanied by the dispersion effect due to the presence of a target gas (e.g., methane, carbon dioxide or nitrogen dioxide) inside the Fabry-Perot cavity.

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Diffraction efficiencies of a reflection-type blazed holographic optical element (HOE) are analyzed and optimized for use in a totally integrated optical head. The HOE, consisting of four-step phase levels, was fabricated by a double-etching process. By controlling each etching depth, signal light power efficiency was maximized to 16% and the power ratio of noise components relative to signal light power was suppressed to 21%. Diffraction efficiencies were made uniform over the entire HOE in oblique positioning by controlling the respective step widths of the HOE.

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A conjugate image plane correlator with holographic disk memory is proposed. Optical correlation between conjugate images reconstructed from a holographic disk and an input image on liquid-crystal television is executed with the rotation of the disk. Regardless of Fourier hologram recording with the pseudorandom diffuser, it is found possible to take out the diffuser from the original hologram recording scheme using an image reconstruction process and to get correlation signals between input and reconstructed conjugate images in the output plane of a two-lens imaging system. Generation of conjugate replicas with high contrast causes exact matching with an input image which results in high recognition performance for autocorrelation signals. The transfer function of an optical system can be controlled by adjustment of either hologram size or hologram area illuminated with a laser beam. Hence, the output intensity distribution can be adjusted by selecting a proper pupil function and the size of an output pupil defined by the input pupil size and the optical system magnification factor. The real-time character recognition by optical parallel high-speed processing for two-dimensional images with position normalization is demonstrated.

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An artificial compound eye corresponding to apposition eyes of insects has been demonstrated using a two-dimensional array of gradient-index rod lenses known as a Selfoc lens plate (a SLP). A single erect MoirEimage is reconstructed from a number of inverted micro-images by an experimental optical system composed of the SLP, a pinhole array and a plano-concave lens. Characteristics of the compound eye is briefly discussed from the viewpoints of space-bandwidth product, viewing angle, and focal depth. Capability of a scale-invariant image sensor that has been proposed as an application of the compound-eye-type imager was also proved experimentally.

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A new algorithm for speckle noise removal from interference patterns is proposed. The method, called cross absolute filter (CAF), is especially well suited for noisy interferograms with phase error pixels. Extensive computer simulations performed on both digitally generated fringes and experimental data show that CAF performs better than classical median-type filters, preserving more subtle details.

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The absorption characteristics of circular double-clad fibers are analyzed in straight and bend cases with geometrical optics and mode coupling theory. A concept of absorbable power ratio is defined to describe absorption behavior and establish a theoretic model. The model investigation indicates that the absorption of doped core is determined by the absorbable power ratio, absorption coefficient, and coupling coefficient. Along with the increase of fiber lengths, the total absorption efficiency tends to saturation. A three-dimensional ray tracing simulation has also been achieved to calculate absorption efficiency and the calculated results are found to agree well with the model on the assumption of inconstant coupling coefficient. To improve the absorption, potential methods such as using proper bend as well as good pump light and bending fiber with variant bend radiuses are also discussed.

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A highly energetic flashlamp-pumped dye laser of 110 J output energy and overall efficiency of 1.1% is developed. For such a powerful laser particular considerations must be taken in order to reduce thermal distortion in the dye solution caused by high-energy pumping. The laser system is therefore composed of a laser head with a four-fold elliptical cylindrical reflector, extended Marx-bank driver circuit, a large aperture dye cell of 44 mm inner diameter and an unstable resonator.

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An active phase-shifting interferometer using current modulation of a laser diode is proposed. Fringe movement in the instrument is detected by a spatial filtering detector whose output is fed back to the injection current of the laser diode to lock the fringes and shift them correctly for phase shifting analysis. Frequency modulation characteristics of the laser diode and frequency response of the feedback system are first investigated. We constructed a portable interferometer head set apart from a mirror under test then measured the shape of a spherical mirror 130 mm in diameter, which was placed on a wooden table subject to vibration. Measurement repeatability of λ/35 was achieved.

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Two-dimensional rotational temperature measurement was performed in a stable combustion flame of premixed butane and oxygen using multiline laser induced fluorescence (LIF) of nitric oxide molecules. Multiple rotational absorption lines of A²Σ⁺←X²Π(0,0) Q₁ and Q₂ lines were excited by laser light around 226 nm, and the LIF signal was observed by an image-intensified digital camera. Temperature was determined through least squares fitting correlation between LIF intensity and excitation rotational quantum number for the Boltzmann distribution function. The measured LIF intensity was approximated by the Boltzmann distribution with good accuracy, and the temperature obtained was between 500 K and 1800 K for the test flame. The measuring error of the temperature was evaluated and found to be 80 K, which corresponded to 8% of the measured fluorescence intensity. The two-line LIF scheme was evaluated by different pairs of excitation lines (Q₁(31.5)/Q₁(16.5) and Q₁(18.5)/Q₁(16.5)) for comparison with the multiline LIF approach. Temperature which was obtained by two-line LIF scheme corresponded well with multiline LIF results for Q₁(31.5)/Q₁(16.5) excitation. However, for Q₁(18.5)/Q₁(16.5) excitation, the obtained temperature did not agree with the multiline LIF result because the population of rotational states J=18.5 and J=16.5 is similar at high temperatures. We found that two-line LIF temperature measurement was reliable when excitation lines were suitably selected.

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We disprove the existence of a family of Bessel beams [J. Durnin, J.J. Miceli, Jr. and J.H. Eberly: Phys. Rev. Lett. 58 (1987) 1499] for any realistic graded-index media.

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The variationality of a weak-form relation for solving guided-mode problems in linear graded-index media is shown to be provable in an intuitive fashion. A connection with variational crimes is discussed.

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