Haruko Takenaka

Focusing Characteristics of High-Efficiency Fresnel Zone Plate Fabricated by Deep Ultraviolet Lithography

The feasibility of using photoresist Fresnel zone plates as micro-optic components was examined experimentally. Deep UV lithography was used to fabricate zone plates with submicron pitch, and nearly diffraction-limited spot formation and high efficiency were achieved. The direct collimation of a semiconductor laser beam was demonstrated.

Double Diffraction of Phase Gratings in the Fresnel Region

Double diffraction of phase gratings in the Fresnel region is studied following the previous paper in which double diffraction of amplitude gratings was reported. For sinusodially modulated gratings, series expansion analysis of the contrast in the periodic change in transmitted light intensity as a function of relative displacement was made and the contrast is shown to reach nearly unity for appropriate amplitude of phase modulation. Experimental results on photoresist gratings are found to coincide qualitatively well with theoretical predictions. For double diffraction of two ultrasonic light modulators the characteristics are shown to depend not only on the modulation depth of ultrasonic wave but also on the widths of ultrasonic columns and the angle of incidence.

Fabrication of high numerical aperture zone plates using deep ultraviolet lithography

Linear zone plates with a minimum linewidth of 0.69 μm are fabricated by electron-beam writing and deep UV lithographic techniques. The focusing characteristics are examined for laser beams at 0.633 and 0.86 μm in wavelength. A focal length of 200 m, minimum spot size of 1.0 μm, and a numerical aperture of 0.42 are obtained at λ = 0.633 μm. Possible applications of the present technology to the fabrication of miniaturized focusing elements for opto-electronics are discussed.

Measurement of mechanical deformation of dielectric fibres by a light scattering method

This paper describes an experimental method to detect quantitative changes of both refractive index and diameter of unclad dielectric fibres, such as fused silica fibre and nylon 6 fibre, due to tensile stress. The technique employed here is based on the variation in the position of a fringe in back-scattered light, which is generated when a laser beam is incident at a right angle to the axis of the fibre. This procedure makes it possible to measure refractive index, diameter and ellipticity to within an accuracy of 0.048%, 2.6% and 0.05%, respectively.

Construction of Photolithographic Phase Gratings Using the Fourier Image Effect

The blurring effect in printing fine grating patterns on photoresist films can be minimized by using the Fourier image effect, which involves the image-forming nature of periodic patterns in the Fresnel region. Experiments using gratings having lattice constants of 3.8 mum and 10 mum are reported. The effectiveness of the Fourier image was confirmed by the evaluation of constructed phase gratings using diffraction efficiency measurements and SEM observations of sectional views. Effects of partial spatial coherence on the quality of gratings are discussed.

Analysis of Two-Dimensional Etching Effect on the Profiles of Fine Holographic Grating Made of Positive Photoresist AZ2400

The present report describes an experimental investigation on diffraction efficiency of holographic gratings made of AZ2400 and the profile pattern of fine gratings (f=1000 lines/mm~2000/lines/mm), together with the numerical analysis of development process taking into account the two-dimensional etching effect. The deviation from sinusoidal profile for increasing development time at higher spatial frequency range is observed by SEM. A tentative model to explain a preferential etching effect with the spatial pattern profile and the change in grating profile with increasing development time is presented. Thus the apparent spatial resolution of holographic grating made of photoresist can be attributed to the side etching effect during the development process.

Measuring Method of Stress Distribution in Models of Fabrics Using Photoelasticity

In the present study the possibility of application of photoelasticity to the measurement of stress distribution in fabrics is investigated. By experimental investigation using photoelastic models which are composed with plane polyvinyl chloride film and have structures like that of various fabrics, distribution of lines of principal stress and principal axes of stress in those models under various loads are determined. By using those photoelastic models of fabrics, it is expected that the mechanical properties of fabrics itself are able to be investigated.

Double Diffraction of Holographic Phase Grating and Its Application to Displacement Measurements

It was pointed out by Burch that blurring due to diffraction in moire type displacement measurement can be minimized by using the Fourier image effect of transmission amplitude gratings. Similar effects can be obtained also by using phase gratings instead of amplitude gratings. The Fourier image and the double diffraction of holographic phase gratings of small grating constants (0.75~10.0 µm) are investigated. Theoretical considerations on the contrast of double diffraction are also presented.