Waveguide polarizers processed by localized plasma etching.

We develop a downstream localized plasma-etching process that permits in situ monitoring of light throughput in a semiconductor-clad channel waveguide as the semiconductor thickness is trimmed. Hydrogenated amorphous silicon films are deposited on ion-exchanged channel waveguides by plasmaenhanced chemical vapor deposition. We then employ the localized plasma-etching process to maximize accurately the extinction ratio between TE and TM polarizations propagating in the clad waveguide. We achieve polarization extinction ratios of greater than 30 dB for both TE-pass and TM-pass polarizers.