Birefringent omnidirectional reflector.

Anisotropic optical coatings offer unique polarizing properties, unmatched by conventional isotropic devices. Here we demonstrate the fabrication of a birefringent omnidirectional reflector, a type of photonic crystal, which exhibits complete reflection of radiation at 1.1 microm for all incidence angles and polarizations. The thin-film device was deposited from electron-beam evaporated silicon, with refractive-index variation arising from atomic-scale porosity created with glancing-angle deposition. Birefringence was found to enhance the performance of the device compared with its isotropic counterpart by enlarging the photonic bandgap region of omnidirectional reflection.