Planar waveguides

摘要

The invention relates to the production of planar optical waveguides which comprise composite path regions, e.g. for lasers. A layer (12) of a first glass composition is deposited, and selectively etched to remove unwanted material so as to leave behind path regions. A second glass composition (13) is deposited in the form of a soot. The amount of the second glass composition (13) is calculated to replace the amount of removed material whereby sintering melts the second glass composition (13) to fill the space created by said selective etching. This produces a composite layer which comprises said second glass composition (13) optically connected to the previously deposited path regions. The composite layer is selectively etched to produce interconnected path regions of two different glass compositions. Preferably the first glass composition contains a lasing dopant, e.g. erbium, and the second glass composition contains no lasing dopant.