Thermally reconfigurable loss in a passive optical cavity

Thermo-optic effect is the simplest and most cost-effective method for reconfiguring an optical cavity, but fails to tune the optical loss in an ordinary cavity. By embedding an interferometer within an optical cavity, we demonstrate thermo-optic tuning of the quality factor from 3000 to 10000 and extinction ratio from ~0 dB to 25 dB in a completely passive silicon micro-ring resonator. This is an important step towards realizing cost-effective reconfigurable photonic devices in purely passive waveguide platforms.