Nonlinear optical impairments in silicon ring resonator thermometers and their mitigation

Silicon ring resonators are currently being assessed by several national metrology organizations as thermometers for use in calibration laboratories and in high-accuracy commercial applications. We show that nonlinear refractive index changes due to self-heating and free carrier generation by the interrogating light can be sources of error in temperature measurements with a Si ring-resonator thermometer. Since self-heating and carrier generation depend on material defects and the resonator structure, we show that these effects can be mitigated by optimizing the resonator design and fabrication process.