Reseach On The Property And Mode Selection Technology Of Fiber Coupling Whispering Gallery Mode Microsphere Cavity

The Whispering Gallery Mode(WGM)microcavity is widely used in the filed of optical communication and sensing,for its high quality factor,high cavity energy density and narrow transmission line width.As an indispensable device in optical communication network,the mode-selecting filter plays an essential role in improving the transmission rate and the signal-to-noise ratio of information.In addition,WGM microcavity is extremely sensitive to the change of ambient media,which makes it extensively used in the field of sensing.This paper concentrate on the study of all-optical tuning property of WGM microsphere cavity mode-selecting filter,as well as the enhancement of surface plasmon resonance(SPR)effect combined with WGM hybrid microsphere cavity.This paper first reviews the research advances and the types of WGM microcavity,the application field and the tuning methods are also introduced.Then the electromagnetic field theory and characteristic parameters of WGM microsphere cavity are briefly discussed.On the basis of microsphere-tapered fiber coupling theory,a finite element model of microsphere-taper fiber coupling system is established to study the effect of pure dielectric microsphere parameters and coupling conditions on the resonance characteristics of WGM transmission spectrum.Then,the hybrid dielectric microsphere which has higher Q factor and narrower bandwidth is also studied,and the parameters of the hybrid dielectric microsphere cavity are optimized.A SPR enhanced WGM hybrid dielectric microcavity sensor is proposed and thhe sensitivity of the proposed sensor is improved compared with exsisting sensors.In this paper,the surface roughness of two microspheres made by arc discharge and CO2 laser are measured,the Q factor of the latter is determined to be 107.The experiment results of coupling efficiency of over 90% and the Q factor of about 2.1 × 107 are achieved with high precision displacement platform,and the 3dB bandwidth at 1550 nm region is 1.2 pm.On the basis of those,the experimental system of the fiber laser based on WGM microsphere mode-selecting filter was established.At 1550 nm region,the all-fiber laser output of 200 mW output power,0.01 nm 3 d B bandwidth,38 dB side-mode suppression ratio and 60 pm all-optical tuning are realized.