The propagation constant, the effective index, the effective guide thickness and the refractive index has been measured by using the method of a variable spacing of a high-index film and the waveguide surface. The spacing can be varied by the electrostrictive element.

Optical waveguide polarizers are realized by three dimensional polymer thin film waveguides with a-Si: H film clad. It has a low index buffer layer between the waveguide and a-Si: H film clad. It is experimentally found that a high extinction ratio for either TE or TM mode pass polarizer can be obtained by changing the hickness of the a-Si: H film clad.

A new fabrication method of a star coupler has been described. It is fabricated by stacking polymer films and then sticking them by a heat press. Using this method, the star coupler can be produced very easily and has square core cross sections. The 5-port multimode star coupler made on an experimental basis has an output power variation of 0.9 dB and an insertion loss of 3 dB.

We fabricated a-Si: H thin films outside the microwave discharge plasma and we varied the substrate bias to investigate the effect of ion bombardments of the film surface. Dark conductivity of the film decreases with increasing negative bias of the substrate with no dependence on the substrate temperature.

A multimode variable directional coupler has been fabricated by piling up films. It uses an electrostrictive element. The output powers can be continuously controlled over a wide range. The output powers from the two output ports of the coupler were equalized at a stress of 16.8 kg/cm2, and the loss due to the stress was small (0.19 dB).

We have fabricated SiN films with stoichiometric composition by double tubed coaxial line type microwave plasm chemical vapor deposition and have discussed the effects of the microwave power on the film qualities.

Light intensity variation is performed in a multilayer optical circuit element consisting of stacked crossing thin film optical waveguides. The principle of operation is the interference of two guided light waves coupled with each other at the intersection of the waveguide of the optical circuit element. Measurements are carried out for each case of the coupling coefficient of the optical circuit element equal to 3 dB and not equal to 3 dB. The percentage variation obtained is 45%.