Investigation Of Lasing And Nonlinearity Characteristics On Compound Glass Whispering-gallery Mode Microcavities

The light from an external source is coupled into a microcavity resonator through a prism or a tapered fiber via the evanescent wave interaction,and the light propagating near the sufcace of the microcatiy is referred as whispering gallery mode（WGM）,the optical microcavity resonator based on the whispering gallery mode has high uniformity,small structrure size,extremely quality（Q）factor and small mode volume,which benefit to the strong interaction between the photons and matter in the glass cavity.Compared with the silica material widely used in modern photonics technology,the microcavity resonators based on the compound glass combine the advantages of tranditional microcavity resonators and compound glass materials,which have attracted much attention from domestic and foreign scholars in recent years due to its excellent optical properties,such as good rare earth ions doping ability,wider infrared spectrum and fluorescence spectrum range,lower phonon energy and higher nonlinear coefficient,etc.So it has important applications in the fields of mid-infrared microcavity lasers,high nonlinear effects,highly doping concentration of rare earth ions,and high-efficiency photoluminescence.This thesis mainly investigated the lasing and nonlinearity effect based on compound glass whispering-gallery microcavities,which are of great value and significance for the design and application of compound microcavities.The main work contents are as follows:1.To solve the basic theory in the microcavity,the spherical coordinate system was substituted into the Maxwell equations,the transverse electric mode and transverse magnetic mode in the microsphere cavity at different polarization states were obtained.Then the electric field distribution under different azimuth angles and radial mode orders was analyzed,and the relationship between the cavity quality factor and the intrinsic frequency was deduced.Finally,a coupling system between the microsphere cavity and the tapered fiber was established,and the relationship between the normalized transmittance and the quality factor was obtained.2.Firstly,a bulk Ho³⁺-doped tellurite glass was prepared,and the absorption spectrum,emission spectrum and fluorescence lifetime were characterized.Then a tellurite glass microsphere was prepared using a CO₂ laser,and a high-transmittance silica tapered fiber with a diameter of～1.3μm was made using a ceramic heater.The Q-factor was measured by scanning the frequency of a 1550 nm tunable laser,the value is about 2×10⁶.In addition,the microsphere was pumped using a single-mode fiber laser at 1150 nm,yielding the 2μm laser output with a low-threshold of 342μW.3.A tunable tellurite glass microbubble structure is proposed.Firstly,A tellurite glass microcapillary with a diameter of～15μm was prepared using fiber drawing tower and microceramic heater.Then the tellurite glass microbubble resonators with a diameter of 150μm and a wall thickness of 670 nm were successfully fabricated by applying air pressure.The Q-factor was measured as 2.3×10⁶.Finally,in the passive microbubble cavity,the temperature sensitivity was measured to be 4.9 GHz/K using a 980 nm diode laser as the pump,and the pressure sensitivity was 7.1 GHz/bar.For the active microbubble cavity,a 980 nm diode laser was used as the pump light,the maximum wavelength tuning range was 1.53 nm,and the sensitivity of the output laser frequency to air pressure was 6.5 GHz/bar.4.The chalcogenide glass with ultra-high nonlinear coefficient is used as the substrate of the microsphere cavity to study the nonlinear effect in compound glass microcavity.The high-purity chalcogenide glass and optical fiber were prepared and characterized,and then the chalcogenide glass microsphere cavity was prepared by using CO₂ laser and ceramic heater.The Q-factor was measured as 2.1×10⁷ at 1550 nm band.Then the stimulated Raman scattering and photomechanical vibration induced by breathing mode were observed.The beat frequencies of the forward acoustic signal and the backward acoustic signal frequency were measured as 80MHz and 7.82 GHz respectively.The measured excitation threshold was 344μW,and the Stokes light conversion efficiency was 7.72%.In this thesis,a 2μm low-threshold microcavity laser based on a tellurite glass microsphere and a tunable tellurite glass microbubble resonator structure is realized.Then the chalcogenide glass with a higher nonlinear coefficient is used as the substrate of the microsphere cavity to study the nonlinear effect in the compound glass optical microcavity.In summary,the work of this thesis has important significance for the research of compound glass optical microcavity based on WGM in the field of lasing and nonlinear effect.