Experimental Studies On Micro-resonator With Whispering-gallery Modes Coupled By Tapered Fiber

In recent years,optical microcavities such as microcylinder,microdisk, microring,microsphere have been greatly developed in microcavity laser and spectrum technology.In this thesis,the microsphere/microcylinder and the tapered fiber coupling system,are regarded as the object of study.The discrete structural resonance in the silica microsphere/microcylinder and glass microsphere doped by Er3+ is experimentally observed.Then we studied more about the characteristics of the resonance.This thesis consists of the following five parts of work.Firstly,we had a brief review on the history of microsphere/microcylinder resonance in theoretical and experimental studies.Then we introduced simply the applications of the microcavity.Secondly,according to the Mie's scattering theory,the optical field in a microsphere has been obtained.The characteristics of the microspherical resonance and the biconical tapered fiber have been analyzed separately.The theory of microsphere has been approximately applied to the study of microcylinder.Then the field solution of biconical tapered fiber has been obtained.Next,the coupling system between microsphere and tapered fiber has been analyzed theoretically.The transmission ratio of the coupling system and its dependence on the gap between microsphere and biconical tapered fiber have been discussed.The coupling system consists of critical coupling,excess coupling and deficient coupling.And next,the CO₂ laser system of drawing the biconical tapered fiber has been designed,and the biconical tapered fiber that we need has been made.Then we improved the system to fabricate silica microsphere/microcylinder.Using the Er³⁺-doped phosphate bulk glass,the Er³⁺-doped phosphate glass microsphere is fabricated by this CO₂ laser system.At last,the coupling system has been set up.The laser light is coupled into the silica microsphere by a biconical tapered fiber.The discrete structural resonance in the absorption spectra was observed,and then the splitting effects of the modes were analyzed.Then the coupling experiment of Er³⁺-doped phosphate glass microsphere with biconical tapered fiber has been studied in detail.The measured wavelengths,the interval between the adjacent modes and the feedback have been compared with the theoretical computation,and they are fair coincident with each other.Lastly,the coupling of microcylinder and biconical tapered fiber has been studied briefly.The research of this dissertation is supported by National Natural Science Foundation of China.number 60277026.