| Optical microcavities are typical optical devices that have received widespread attention in various fields,such as nonlinear optics,integrated optics,quantum optics,and highsensitivity sensors,due to their small mode volume,low optical loss,and compact structure.In these applications,traditional electronic locking uses devices such as signal generators,phase modulators,and PID controllers to achieve laser closed-loop locking,which has the advantages of high locking accuracy and good locking effect,but the system is complex,requires many devices,and is difficult to integrate.In contrast,thermal mode locking of optical microcavities uses the ability of a broadened peak to self-sustain stability to achieve mode locking,with the advantages of small system size,integrability,and autonomous locking.The use of optical microcavities for thermal mode locking has broad application prospects.This article focuses on the theoretical and experimental study of thermal mode locking of optical microsphere and optical microbubble cavities coupled with optical fibers.Optimization schemes based on the thermal mode locking performance of optical microsphere and optical microbubble cavities are proposed,and specific research content includes:(1)Analyzing the thermal nonlinearity effect locking mechanism of optical microcavities and establishing a coupling structure model of an optical resonant cavity.The optical transmission characteristics of the optical resonant cavity were analyzed using the transfer matrix method,and the relevant performance parameters of the optical resonant cavity were discussed.By analyzing the thermal transfer mechanism of the optical microcavity,the factors affecting the thermal mode locking time and stability were obtained.(2)Optical microsphere cavities were prepared using high-temperature melting and cooling method,while optical micro-bottle cavities were fabricated using arc discharge method.Cone-shaped optical fibers were produced using thermal stretching method.A coupling system of optical microcavity and cone-shaped optical fiber was built to analyze the basic characteristics of both in experiments,with real-time observation of the coupling state.(3)A thermodynamic model was established inside the optical microsphere cavity,and the thermal nonlinear effect inside the cavity was theoretically analyzed.Relevant parameters that affect thermal nonlinear locking were investigated.Stability verification of thermal nonlinear locking under different parameters was conducted experimentally,demonstrating the correctness of the model.The optimal parameters for thermal mode locking were obtained as follows: the diameter of the optical microsphere cavity was 52μm,the scanning speed was1.12 Hz,and the pump light power was 150 mV.A method of tuning the thermal mode locking time based on microsphere cavity parameters was proposed,which improved the locking accuracy and extended the locking time from 0.5h to 1.1h.The oscillation amplitude was reduced from 16 mV to 10 mV.(4)To improve the thermal mode locking performance of the micro-bottle cavity,a copper cobalt oxide micro-bottle cavity was prepared by injecting copper cobalt oxide and drying.Metal particles were used to absorb photons inside the cavity to reduce the light intensity and improve the thermal mode locking performance.An optimization scheme for thermal mode locking based on the copper cobalt oxide micro-bottle cavity was proposed.Allan variance analysis was conducted to investigate the effects of pump light power and micro-bottle size on thermal mode locking,and the optimal parameters for thermal mode locking were obtained theoretically as follows: the pump light power was 160 mV and the micro-bottle diameter was 165μm.After injecting copper cobalt oxide,the response of the micro-bottle cavity to parameters decreased,and the thermal mode locking performance improved.The lock-in time has increased from 1.35 h to 1.97 h,and the oscillation amplitude has decreased from 7.2mV to 6.4mV in an optical microcavity。... |
