INTEGRATED-OPTIC RING RESONATORS WITH 2 STACKED LAYERS OF SILICA WAVE-GUIDE ON SI

A ring resonator with a radius of 1.5 mm is demonstrated using a stack structure consisting of two layers of GeO2-doped silica waveguide with different refractive index differences (DELTA). One is a high-DELTA waveguide layer with a DELTA of 2% for a small-radius ring and the other is a waveguide layer with a DELTA of 0.75% for good fiber coupling. The waveguides and a flattened middle-cladding layer are stacked on a Si substrate. The ring resonator exhibited a wide free spectral range (FSR) of 21.6 +/- 0.1 GHz and a high finesse of 110 +/- 10.