Loss reduction in electromechanically tunable microring cavities

Nanophotonic structures coupled with mechanics enable large effective index perturbation. To date, however, the relation between index tuning and induced optical loss has not been considered in detail. In this work we present an in-depth study of optical loss mechanisms in an electromechanically-tunable waveguide filter. Gradient electric forces modify the coupling between a microring optical cavity and a suspended micromechanical (MEMS) perturber resulting in a measured tuning greater than one free-spectral range (FSR) and an effective index tuning of 3×10 -2 . We examine various loss contributions and find, for certain conditions, a surprising reduction in loss with greater MEMS-induced mode perturbation. Modeling confirms the device behavior and loss mitigation is discussed.