Low-loss photonic waveguides and ring resonators and a method for low-loss photonic waveguide and ring resonator fabrication

Abstract

Low loss photonic waveguides and ring resonators are necessary for highly accurate gyroscope functionality. For fabrication of these low loss waveguides and ring resonators, an improved and cost-effective fabrication method has been proposed wherein for silicon nitride waveguides, a minimum of 2 μm thin bottom oxide cladding above etched trenches (cavities) in silicon facilitates both lower losses and higher Q values ring resonators as compared to the conventional 8 μm thick bottom oxide cladding without etched trenches in silicon. The trenches below the thin bottom oxide cladding are created through xenon difluoride (XeF2) gas etching in selective areas of silicon substrate through vias (openings). After etching the trenches, these vias are filled by the addition of a final top oxide cladding layer. The proposed method provides about three times improvement both in propagation losses as well as in quality factor for side coupled ring resonators.