Silica-based finesse-variable ring resonator

A finesse-variable ring resonator with a free spectral range of 2.5 GHz is demonstrated using silica-based optical waveguides. The finesse is controlled with a coupling-ratio-variable coupler, which is composed of a symmetrical Mach-Zehnder interferometer and thermooptic phase shifters. The finesse of the resonator is changed continuously from 6 to 27.<
>