Independently reconfigurable internal loss and resonance-shift in an interferometer-embedded optical cavity
Optical cavities find diverse uses in lasers, frequency combs, optomechanics, and optical signal processors. Complete reconfigurability of the resonant frequency as well as the loss enables development of generic field programmable cavities for achieving the desired performance in these applications. Conventional reconfigurable cavities are generally limited to specific material platforms or specific optical tuning methods and require sophisticated fabrication. Furthermore, the tuning of the loss is coupled to the resonance-shift in the cavity. We propose and demonstrate a simple and generic interferometer in a cavity structure that enables quasiperiodic modification of the internal cavity loss and the cavity resonance to reconfigure the Q-factor, transmission characteristics, and group delay of the hybrid cavity, with simple tuning of the optical phase in the interferometer. We also demonstrate methods to decouple the tuning of the loss from the resonance-shift, that enables resonance-locked reconfigurability. This structure also enables resonance-shift to both shorter and longer wavelengths using the same phase-tuning technique, which is challenging to achieve in conventional reconfigurable cavities. These devices can be implemented in any guided-wave platform (on-chip or fiber-optic) with potential applications in programmable photonics and reconfigurable optomechanics.