Single Ring Interferometer Configuration With Doubled Free-Spectral Range

We proposed and experimentally demonstrated a single ring interferometer configuration that produces doubled free-spectral range (FSR) by in-phase combining light from the pass-through port and drop port of the resonator. It exhibits higher extinction ratio than conventional single ring resonators, brings no additional stress to fabrication, works for both polarizations, and does not require any particular design on the ring structure. By using this configuration, a wide FSR can be obtained while maintaining a high quality factor.