High-Q Microresonator Characterization By Optical Frequency Domain Reflectometry

We demonstrate a novel approach to characterize the microresonators using optical frequency domain reflectometry (OFDR). We analyzed the microresonators in both the spatial and spectral domains by a modified OFDR, which can reach a sensitivity of -130dB. We also provide a model to extract the free spectral range (FSR) of a microresonator from the backscattered signal. We fabricated three silica microresonators with different coupling conditions. The transmission differences between these samples can be shown clearly in the distributed loss curves. The power attenuation factor and the relative coupling strength of the microresonator can be derived from the OFDR data.