Sol-gel synthesis of one-dimensional photonic bandgap structures

Abstract

A series of one-dimensional photonic bandgap devices were fabricated using SiO2 and TiO2 films deposited from solution by the sol-gel method. A dielectric mirror, or broadband interference filter, was fabricated by alternating quarter-wave optical thickness layers of the two films on a silicon substrate for a total of six layer pairs. This device exhibited an omnidirectional photonic bandgap of 450 nm in TE-polarization and 110 nm in TM-polarization. A microcavity, or narrowband filter, was fabricated with a TiO2 Fabry-Perot cavity sandwiched between two mirrors of three layer pairs each. The resonant cavity corresponded to a wavelength of roughly 1500 nm and shifted to shorter wavelengths with increasing incident angles. A maximum resonant quality factor of 11. 7 was achieved.