Analysis and fabrication of hybrid metal-dielectric omnidirectional Bragg reflectors

We describe chalcogenide glass and polymer based Bragg reflectors with a metallic underlayer and use a transfer matrix model to analyze their performance. The angle-averaged reflectance of a hybrid mirror approaches unity for only a few periods and is much higher than that for a nonmetallized Bragg reflector or for the metallic layer alone. For an angle-averaged reflectance greater than 0.99, the addition of a metallic underlayer enables nearly a tripling of the omnidirectional bandwidth (from approximately 110 to approximately 305 nm) concurrent with a significant reduction in the number of required periods (from 10.5 to 4.5). Hybrid mirrors of 4.5 periods, with a 50 nm Au underlayer and overall thickness of approximately 2 microm, were fabricated atop silicon substrates and characterized. They exhibit an omnidirectional stop band in the 1450-1750 nm wavelength range, in good agreement with theoretical predictions.