Applications Of Tunable Silica Whispering-gallery-mode Optical Microresonators

Whispering-gallery-mode optical microcavities have been paid more and more attention in optical research field due to their ultra-high quality factors,small mode volumes and easy preparation.Their quality factors surpass the traditional optical cavity several orders of magnitude,greatly enhancing the interaction between light and matter,providing a new platform for photonics device research.In many of its applications,tunability is an important performance parameter.In this paper,we introduce the mircobottle cavity and microsphere cavity,including their basic theory,coupling characteristics and fabrication.And the application in tunable ultra-narrow linewidth laser and tunable polarization beam splitter are introduced.The main content of the thesis includes:(1)The research background of whispering gallery mode is introduced,and research highlights on tunable microcavity and its application are summarized.The optical field distribution of the microsphere cavity and the microbottle cavity is analyzed.And the coupling theory and backscattering of the whispering gallery mode microcavity are introduced.(2)A narrow linewidth laser based on microbubble-based all-optical tuning is proposed.The preparation and testing methods of tunable micro-bottle cavity are introduced and applied to the fiber laser loop to achieve a tuning range of 2.7 nm and an ultra-narrow linewidth laser of 500 Hz.(3)An all-optically tuned polarization beam splitter based on magnetic fluid microspheres is proposed.Based on the theoretical analysis of the polarization-related properties of the microsphere cavity,using the add-drop model constructed by the combination of microfiber and microsphere cavity,the separated orthogonally polarized beams are obtained in the device.The separation ratio exceeds 20 dB,and the all-optical tuning range reaches 5.5 nm.