2ND-ORDER FILTERING AND SENSING WITH PARTIALLY COUPLED TRAVELING WAVES IN A SINGLE RESONATOR

The counterpropagating waves in a single traveling-wave cavity can be partially coupled by means of a small perturbation such as a notch. Wh en it is side coupled to a waveguide, this single cavity yields a gene ral second-order (Chebyshev) reflection response in the waveguide, whi ch is useful for narrow-bandwidth reflecting applications. In a differ ent application, the cavity amplifies small reflections induced by ext ernal perturbations, thus finding use in ultrafine sensing. Amplificat ion factors as great as 10(12) are predicted for the highest-Q microsp here resonators. The analytic theory of these devices is presented. (C ) 1998 Optical Society of America.