Quality of a-Si : H/Si3N4 multilayer films fabricated by double tubed coaxial line type MPCVD system and application of the films to optical circuit element

The object of this research was the fabrication of high-quality a-Si:H/Si3N 4 multilayer films with ultrathin multilayered configurations to serve as a new photonic material, as well as the evaluation of the film quality and a pplications to photonics. The authors have succeeded in controlling the thi ckness of the multilayer film at subnanometer order as indicated by the X-r ay diffraction peak of the a-Si:H/Si3N4 multilayer film. The theoretical cu rve and the experimental results for the optical energy band gap agree well for multilayer films fabricated by varying the thickness of the a-Si:H lay er while the thickness of the Si3N4 layer is kept constant, and hence excel lent multilayer films are obtained. These multilayer films are applied to o ptical waveguides. The optical waveguide with an ultrathin multilayer struc ture, much thinner than the wavelength lambda of the guided light, is expec ted to exhibit an anomalous propagation characteristic. It is found that th e TM mode is transmitted while the TE mode is cut off in the present multil ayer slab waveguide. (C) 2001 Scripta Technica.