Type II high-strength Bragg grating waveguides photowritten with ultrashort laser pulses.

A one-step type II photosensitivity process has been optimized for inscribing strong >30-dB first-order Bragg-gratings during laser formation of buried waveguides in borosilicate glass. Mode profiles, propagation losses, waveguide birefringence and transmission and reflection spectra were systematically studied in the 1550-nm telecom band over a wide range of laser exposure conditions. Low-loss and birefringence-free waveguides are reported for a narrow laser processing window of 1.0 +/- 0.2 ps pulse duration, yielding highly stable Bragg resonances to temperatures up to 500 degrees C.