Studies In Optical Ring Resonators With High Polarization Extinction Ratio

Resonant Optic Gyro is a novel angular velocity sensor based on the Sagnac effect, which has great advantages in miniaturization and integration. As the sensing element of the ROG, the optic ring resonator is required to be of low loss, high finesse and high polarization extinction ratio (PER). In the ring resonator, there are two eigenstate of polarizations (ESOPs). Due to the environmental factors, these two ESOPs fluctuate individually, and then induce error in the gyro output. The polarization-fluctuation induced error is one of the main optical errors in the ring resonator. To eliminate the influence of the polarization-fluctuation induced error, the dissertation has made some studies on the optic ring resonator with high PER. Specifically, the main works in the dissertation are as follows.By estimating the effect of ESOP fluctuating on the resonace curve, the influence of the polarization-fluctuation induced error is evaluated by the variation of the resonance depth and the full-width-half-maximum; the high PER is achieved by either improving the directional coupler or integrating the in-line polarizers, the effects of these two technologies are calculated and compared; according to the analysis, the effect of the PER at the coupler is similar to, but a little higher than that of the PER at the in-line polarizers.To the fiber resonator, a single-polarization resonator based on photonic bandgap fiber (PBF) is designed. By utilizing the coupling coefficient abnormality phenomenon, this resonator realizes single-polarization coupling in certain conditions; by calculating the overlap integral of the guided mode fields, the negative phase region of the guided mode of PBF is prooved to be the essential reseaon of the coupling coefficient abnormality phenomenon; using finite element method, the optimized structure paremeters for single-polarization coupling is acquired, and the effect of angular misalignment is estimated. When the angular misalignment is contorlled under0.9degree, the PER can be higher than30dB.To the waveguide resonator, by utilizing the Brewster principle and tilted waveguide gratings, a waveguide resonator with high PER is designed. By appling Volume Current Method to the orthogonal coordinates, the scattering fields and the PERs of two types of TWG are calculated, the index profile of which is sinusoidal and step-index, respectively. According to the analysis, while the tilting angle of the TWG is equal to the Brewster angle, the period of the TWG satisfies the phase matching condition, its PER can reache the maximum. While the amplitude of index variation in the TWG is0.005, the PER of the sinusoidal TWG is844.54dB/m, and that of the step-index TWG is961.48dB/m.The works mentioned above can be the theory basis and the technical reference of the further studies of the optical ring resonators with high PER.