Integrated Optical Ring Resonator

Resonator Optic Gyro (ROG) is a novel optical sensor, which is used to measure the rotation rate due to the resonance frequency difference based on the optical Sagnac effect. Resonator Integrated Optic Gyro (R-IOG) adopts advanced micro and nano integrated optoelectronic technique, whose ring resonator is made by optical integrated circuit. The R-IOG has many advantages in miniaturization and integration compared with Interferometic Optic Gyro (IOG) or Ring Laser Gyro (RLG). The Integrated Optical Ring Resonator (IORR) is the core-sensing element of the R-IOG, so it is the key to design and manufacture this kind of gyro. Based on the application of R-IOG, the resonance characteristics of the IORR and multi-turn ring resonator and polarization fluctuation are studied in this paper. Also some one turn and multi-turn IORRs with different coupling coefficients are designed and fabricated. Use the fabcaited IORR as the sensing element, the gyro signal of the R-IOG is observed successfully. The main works of this thesis are as following.The resonance curve expression of the IORR is derived using the optical field overlapping method, and the relationship between the basic structure parameters and resonance characteristic is studied. One reference straight waveguide with the same waveguide structure as the IORR is designed to get the maximum of the transfer coefficient of the ring resonator through comparing the output voltages. The finesse and extinction ratio of IORR can be obtained by measuring the resonance curve. So the model of measuring the basic structure parameters of the IORR nondestructively is set up, including waveguide propagation loss, coupling coefficient and excess loss of directional coupler. After above analysis, the influence of the basic structure parameters on the limited sensitivity of the R-IOG system is analyzed. It is found that the limited sensitivity can be improved by increasing the number of turns of the IORR based on the premise that the loss meets the challenge.Using the Fresnel diffraction theory, a universal model used to calculate the excess loss of the crossed waveguide is set up. Simultaneously, the relationship between the excess loss and the intersection angle is obtained according to the finite difference beam propagation method. On this basis, some crossed waveguides with different insection angles are fabricated to verify above theoretical results. The excess loss of crossed waveguide in multi-turn IORR is measured nondestructively through comparing the resonance characteristics of one turn and two turn IORRs. Furthermore, the influence of the multi-turn ring resonator over the limited sensitivity of R-IOG is analyzed. Based on the above analysis, only when the excess loss is lower than a critical value, the limited sensitivity can be improved by introducing multi-turn IORR into R-IOG. That is to say, there are a best coupling coefficient and a best number of turns to get highest limited sensitivity of R-IOG.This paper also presents the polarization fluctuation in the IORR, especially the influence of the temperature fluctuation over polarization characteristic. The polarization analysis model is set up using Jones Matrix. Throngh this model, we can analyze the influence of the structure parameters over polarization characteristic in IORR. Also the controlling temperature indexes of locking technique requirement of the R-IOG can be obtained through this model.The one turn and multi-turn IORRs with different coupling coefficients are fabricated on silicon substrate by low-pressure chemical vapor deposition method and reactive ion etching. The one turn IORR includes the single-mode waveguide type IORR and polarization-maintain IORR. The resonance curves of these IORRs are measured. The finesse of one turn IORR is 67.7 and polarization extinction ratio is 21.4dB. The finesses of two turn and four turn IORR are 19.3 and 10.0 respectively, because the excess loss of the crossed waveguide with insection angle of 20°is too high. At the same time, the gyro signal of the R-IOG with the fabricated IORR as the key sensing element was observed successfully.