Unidirectional, Efficiency-Controlled Coupling from Microcavity Using Reflection Feedback

We propose a microcavity-to-waveguide side coupling system with a reflector at one end of the waveguide for the feedback. Using this system, one can get a unidirectional output from a microcavity-based light emitter, where the output coupling efficiency and the cavity loss can be enhanced or suppressed through tuning optical phase of the feedback. Theoretical calculations are confirmed by finite-difference time domain (FDTD) simulation of the coupling between a photonic crystal cavity and a microfiber with a perfect mirror attached. Unidirectional coupling from the photonic crystal cavity to the fiber with efficiency of 90% is demonstrated in the simulation