Preparation of VO2 thin film and its direct optical bit recording characteristics.

Vanadium dioxide (VO2) film which has nearly the same transition point as single crystal has been obtained by reactive evaporation of vanadium on glass and subsequent annealing in N2 gas. Relations between optical properties of V02 film and its preparation conditions are presented. We made optical direct bit recording on V02 film using a laser diode as the light source. The threshold recording energy and bit density are 2 mJ/cm 2 and 350 bits/mm, respectively. We also made tungsten doping to lower the V02 film transition temperature.

Light deflector using a chalcogenide amorphous loaded LiNbO(3) waveguide.

A large-angle Bragg deflector has been demonstrated, utilizing the photoinduced refractive-index change in an As-Se-S-Ge amorphous film loaded on a Ti-diffused LiNbO(3) waveguide. Modal analysis shows that optical fields and effective indices in a LiNbO(3) wavelength are affected strongly through the index change in the amorphous overlayer. Coupling coefficient and interaction length of the deflector are derived analytically by the coupled wave theory. Interaction length becomes short rapidly with increasing the refractive-index change of the grating or the loaded film thickness. An almost 40 degrees deflection has been achieved experimentally with a 0.7-microm grating pitch and 1-mm interaction length.

Waveguiding properties of (Se,S)-based chalcogenide glass films and some applications to optical waveguide devices.

Fundamental waveguiding properties of As-Se-S-Ge chalcogenide glass films and some applications to passive waveguide components are presented. The refractive index of the chalcogenide glass film annealed just below the glass transition temperature (200 degrees C) increases by light irradiation near the absorption edge. The refractive-index change amounted to 0.03 at 1.06 microm. The propagation loss of 0.4 dB/cm has been achieved at 1-microm thickness for As(40)Se(10)S(40)Ge(10) glass film. The photoinduced refractive-index change in the chalcogenide glass film was large enough to be applied to making passive waveguide components. The curved waveguide and optical directional coupler were designed as passive components.

Strip-loaded waveguide formed in a graded-index LiNbO(3) planar waveguide.

An As(40)Se(50-x)S(x)Ge(10) film strip loaded waveguide, formed in the graded-index LiNbO(3) planar waveguide, has been demonstrated. Analytical results show that the optical field confinement in the waveguide loaded by the high refractive index film becomes large near the film cutoff thickness for the fundamental mode. Photostructural effect of the chalcogenide glass overcomes difficulty in precisely controlling film thickness. A 3-D waveguide has been achieved by loading As(40) Se(10)S(40)Ge(10) film 10 microm wide on a Ti diffused LiNbO(3) planar waveguide. Optical confinement in the waveguide has been improved intensively with the aid of the photostructural effect of the film.

Properties of (Se,S)-based chalcogenide glass films, and an application to a holographic supermicrofiche.

In a (Se,S)-based chalcogenide glass system, the optical property, such as transmission and refractive index, changes reversibly within amorphous phase when the sample is heated and light irradiated. The refractive index in the light-irradiated state is larger than that in the heated state, and the amount of change Deltan reaches 0.05 ~ 0.1 in the visible wavelength region. The merits of this glass system as a recording material are high resolving power and rewritability. As an application, a rewritable holographic supermicrofiche, which is partially refreshable, and its experimental system are given. Characteristic features of this material as applied to an information retrieval system are discussed.