Integrated-optic ring resonators with two stacked layers of silica waveguide on Si

A ring resonator with a radius of 1.5 mm is demonstrated using a stack structure consisting of two layers of GeO/sub 2/-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+or-0.1 GHz and a high finesse of 110+or-10.<
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