Abstract

Photosensitivity in (predominantly) germanium doped fibres and planar waveguide structures is the subject of intense current interest. Permanent refractive index gratings, written using UV light from either pulsed or c.w. laser sources, can be produced by interferometric exposure, yielding Δn values ranging from 10^-5 to 10^-3. Additional techniques such as hydrogen loading, or flame brushing, can further increase this value to ~10^-2. In this paper, we report our studies of planar waveguides of lead germanate glass, grown by Pulsed Laser Deposition. The films are grown under various partial pressures of oxygen, and show distinct and systematic differences in colour, waveguide loss and photosensitivity. We interpret our results in the context of induced oxygen vacancies produced during the growth.

© 1998 IEEE