Grating structures with phase mask period in silica-on-silicon planar waveguides

Direct writing in planar waveguide silica-on-silicon material using a phase mask designed to produce 1550 nm Bragg gratings results in a damage gratin g with a period equal to the similar to 1 mu m phase mask period. This does not agree with the expected period of similar to 0.5 mu m for a first orde r diffraction grating satisfying the Bragg condition when the phase mask ze ro order is less than a few percent of the input beam. (C) 1999 Elsevier Sc ience B.V. All rights reserved.