Characteristics of an integrated optics ring resonator fabricated in glass

We report observation of resonance in a ring waveguide 4 cm in diameter fabricated by ion exchange in glass. The observed finesse of four was explained in terms of loss per unit length and coupling efficiency onto and off of the ring. A large nonresonant background was attributed to mode-mixing in the multimode ring and to an observed depolarization. The ability to measure resonance in a multimode waveguide ring was due to the fact that only the highest order mode was directionally coupled out. Estimates predict finesses of better than 20 making possible the measurement of frequency deviations to 10^-4Å, and temperature variations to 0.002°C. With improvements, this may also be a viable device for inertial rotation sensing.