a-Si:H film on side-polished fiber as optical polarizer and narrow-band filter

An optical waveguide structure consisting of side-polished single-mode fiber covered with thin a-Si:H planar waveguide is studied as a channel-dropping narrow-band filter and fiber-optic polarizer. Spectral and polarization characteristics of the structure are measured in the wavelength region of 600-1600 nm, for the different values of the a-Si:H film thickness and the superstrate refractive index. The FWHM of the filter is about 8 nm for the asymmetric waveguide and 10 nm for the symmetric one. The discrimination of the resonance minima for two polarizations varies from several tens for the symmetric PWG up to several hundreds of nanometers for the asymmetric PWG. The optical losses in the off-resonance region are less than 0.3 dB. The measured value of the extinction coefficient of the fiber-optical polarizer is 32.5 dB. (C) 1998 Elsevier Science S.A. All rights reserved.