Research On Mode Coupling In A Tapered Fiber Coupled With A Bottle Optical Microresonator

Whispering-gallery-mode(WGM)optical microresonators,as one of the optical microcavities,have high quality-factor(Q-factor)and small mode volume,which can significantly enhance the interaction between light and matter.Thus,in the fields of micro-laser,bio-sensing,microwave photonic devices,optical nonlinear effects and quantum physics are widely studied.In a tapered fiber coupled with a WGM microresonator system,there is a mode coupling phenomenon.This is important for optical sensing and optical signal processing.However,the mechanism and change rules of the phenomenon are not clarifying.In this paper,the theoretical and experimental research about a tapered fiber coupled with a Bottle microresonator is carried out.The physical model and equation of a tapered fiber coupled with a Bottle microresonator is established,which can generate mode coupling and enhanced Fano resonance phenomenon.Meanwhile,it is revealed the causes and rules of the phenomena.The work accomplished and main points in this thesis are shown as follows:1.The WGM distribution,mode spectrum,free-spectral-range and dispersion characteristics in Bottle microresonators were calculated with analytical method,as well as the mode distribution and rules of the tapered fiber and the adiabatic condition.Based on the coupling equations describing microresonator-tapered fiber coupling system,the transmission characteristics under different coupling conditions were analyzed.2.The fabrication process of Bottle microresonators was studied.The WGM distribution of Bottle microresonators under tapered fiber stimulated were analyzed experimentally.Meanwhile,the fabrication process and differences of the adiabatic tapered fiber and the non-adiabatic tapered fiber were researched.In the pulling process,the high-order fiber mode is generated,and the mode components can be obtained by the short-time Fourier transform analysis of the normalized transmission spectrum.3.The physical model and mode coupling equation of a single-mode tapered fiber coupled with a WGM microresonator were established.Based on the coupled mode equations,the resonance line-shapes and variation rules resulting from different mode coupling conditions were discussed.Experimentally,the mode coupling effects were achieved in an adiabatic tapered fiber coupled with a Bottle microresonator system.The rules and multi-mode coupling were realized.4.The physical model and mode coupling equation of a single-mode tapered fiber coupled with a WGM microresonator to achieve Fano resonance were established.Based on the coupled mode equations,the resonance line-shapes and variation rules resulting from different mode coupling conditions were discussed.Experimentally,the enhanced Fano resonance was achieved in a non-adiabatic tapered fiber coupled with a Bottle microresonator system.Meanwhile,it is demonstrated that the resonance is wavelength-independent and its line shape is tunable.