Formation of a Diffractional Grating by Magnetic Lithograph
A new method to make an optical diffraction grating has been developed using the Bitter method. A periodic magnetic pattern like 0101 ... is written in a magnetic memory medium, and a magnetic fluid is used as magnetic toner to visualize this pattern. To enhance the contrast of the grating, an interfacial active agent in the magnetic fluid is destroyed by a certain organic solvent, and a DC magnetic bias field is applied to the memory medium to thicken the pattern. When a transparent grating is required, Au film is deposited on it as a parting agent after the formation of a magnetic toner pattern. After separation of the epoxy resin film from the memory medium, Au film is chemically etched. A sharp diffraction image is observed by projecting a laser diode onto the diffraction grating. Using this method, an optical grating can easily be made even on a convex or concave surface.
Point source diffraction and its use in an encoder.
Diffraction from a point light source (a laser diode) was studied. The diffraction images were found to be magnified without using a lens and to move corresponding to the displacement of the slit aperture. A digital encoder using this diffraction is proposed to obtain very high resolution without a lens.
Visible GaAlAs V‐channeled substrate inner stripe laser with stabilized mode using p‐GaAs substrate
A new visible laser, the V channeled substrate inner stripe laser, is developed. This laser can internally confine the current into the V‐channel by using a thin n‐GaAs layer grown on the p‐GaAs substrate. cw threshold currents were 35–45 mA in the visible spectral range of 770–790 nm. And highly stable transverse and single longitudinal mode operation were observed because the built‐in optical waveguide was formed within the V channel.