Research On Fabrication And Tunable Performance Of Optical WGM Microcavity

The optical whispering gallery mode(WGM)microcavity has attracted many attentions in the optical field due to its ultra-high Q and small mode volume.In recent years,optical devices based on optical WGM microcavities have been applied to lowthreshold lasers,high-sensitivity sensors,cavity quantum electrodynamics,and nonlinear optics.Tunable performance is significant to WGM microcavity,which can greatly improve the application potential of it in different fields.Using all-optical tuning methods to tune the WGM microcavity is of great significance to the application in alloptical switches,all-optical modulators,tunable filters and other fields.Based on this,this paper mainly studies the all-optical tuning performance of different microcavities.The specific research contents include:1.The mode field distributions of different WGM microcavities are analyzed and the physical significance of performance parameter,including quality factor,mode volume,and resonant frequency are explored;Microfiber is employed as the dielectric waveguide to excite the WGM and its optical transmission characteristics is studied.It is fund that under the same incident light wavelength,the microfiber with smaller diameter has stronger evanescent field.Further,the coupling efficiency between the microfiber and the microcavity is related to the coupling distance between them,which means in order to obtain a high coupling efficiency,it is necessary to precisely control the coupling distance.2.The silica microsphere and microcylinder are prepared by using standard bare optical fiber,and the hybrid polymer micro-bottle cavity is prepared by polydimethylsiloxane(PDMS).The difference between the coupling spectra of different microcavities is studied.It is found that the microsphere WGM presents a dense coupling spectrum due to the existence of multiple high-order modes in experiments.The coupling spectrum of the microcylinder is sparser than that of the microsphere and exhibits good periodicity.The coupling spectrum of the micro-bottle shows diversity with the different coupling positions of the microfiber.The small free spectral range(FSR)of the spectrum makes it possible to achieve tuning of more than one FSR with low pump power.Besides,the temperature sensing performance of the two kinds of material microcavities are explored.The results reveal that the PDMS microbottle has better temperature sensing performance than the silica microsphere.3.The silica microsphere and PDMS micro-bottle are tuned by the all-optical tuning method.Under the condition of external pump light,the tuning efficiency of silica microsphere and PDMS micro-bottle can reach 0.107pm/m W and 5.23pm/m W,respectively.The PDMS micro-bottle is tuned using the internal pump light tuning method,which can achieve a tuning efficiency of up to 68.3pm/m W.Owing to the small FSR of the micro-bottle cavity,more than one FSR can be tuned using two tuning methods,which illustrates the potential advantages of the PDMS micro-bottle cavity in the field of all-optical devices.