Improved technique for the characterization of micro-ring resonator using low coherence measurement

Low-coherence interferometric measurement has been used to investigate optical waveguide devices with high accuracy. By utilizing an incoherent light source, one can generate separate interferogram features for each optical path. The distance between adjacent features of a ring resonator is related to ring length. With small ring radius, the interferogram spectrum exhibits severe cross-interference between adjacent features that hinders one to analyze the optical path individually. We propose a novel technique to overcome the light-source bandwidth limitation by signal-processing technique, which allows one to characterize small radius micro-ring resonator. This technique has been applied to both numerical simulations and experimental data with significant improvement of the extracted ring parameters. The improvements allow one to better understand the wavelength dependency properties of small radius micro-ring resonators.