POLARIZATION INDEPENDENT NARROW-BAND BRAGG REFLECTION GRATINGS MADE WITH SILICA-ON-SILICON WAVE-GUIDES

We report polarization independent Bragg reflectors, centered at 1.55-mu-m and made with silicaon-silicon waveguides. Gratings are etched into the upper core surface and glass doped with boron and phosphorus is used to fill in the grating corrugation and for the top cladding. The Bragg coupling length in these gratings is independent of polarization. Post-processing anneals at temperatures above 780-degrees-C weaken the gratings and can be used to tailor the reflection stop band in the range 15-1.5 angstrom. By etching trenches along the sides of the waveguides, the strain induced birefringence in practically eliminated and the TE and TM reflection peaks overlap to within 0.4 angstrom.