| Optical dielectric microresonators supporting unique whispering gallery modes(WGMs)with ultra-high quality(Q)factors have potential various applications in cavity quantum electrodynamics,nonlinear optics,high-sensitivity sensors,and optoelectronic devices.Mode field distributions of optical microresonators are related to the cavity shape,the refractive index of the microresonator and the waveguide,the coupling method,and the wavelength.Due to ultra-high Q factor,it is easy to accumulate strong electromagnetic field in the cavity and excite nonlinear optics effect.Therefore,the coupling relation and interactions plays an important role in resonant properties and nonlinear optics effect.In this paper,we take up research the effect between several cavity shapes and resonant characteristics and coupling effect relations.This paper concentrates on the study of the mode interaction in the coupling process of the waveguide and microresonators with several shapes.We plan to design high stability package platform,where the microresonator with an ultra-high-Q factor is applied in nonlinear optics.These work will have an important significance and value in the design and application for microresonators.Detailed research contents are as follows:(1)High Q-factor microsphere resonator is considered as basic research platform.The coupling gap between the microsphere and the fiber taper waveguide is finely precisely adjusted to excite the resonant mode.The excitation of resonant mode can be controlled between the coupling states,including under-coupling,critically-coupling,and over-coupling.The resonant spectra measured is basically in accordance with the resonant points of fundamental mode obtained electromagnetic field theory.Especially,for microsphere resonator,an ultra-high value of Q factor as high as>108 is obtained by optimizing coupling condition.(2)A single mode resonator with capillary structure is proposed.A novel micro capillary resonator is fabricated via arc discharge.The capillary structure can suppress high order modes and help us obtain clean resonant spectra with single mode.This provides a great preform for studying spectral characteristics.The Fano resonance effect is studied based on the interference between the fundamental mode and higher order modes of the taper that coupled to the WGMs of the resonator.The Fano resonance effect in the microcapillary-taper coupling system is studied based on the interference between the fundamental mode and higher order modes of the taper that coupled to the WGMs of the resonator with the help of the coupled mode theory.Via scanning the tapered fiber diameter and changing the polarization of the input light,dynamic Fano resonance lineshapes are periodically achieved.These results hold great potential for enhancing sensing performance and nonlinear optical effects.(3)The tuning characteristic of the conical microresonator and the microcapillary resonantor are experimentally demonstrated.The resonant wavelengths can be tuned by choosing different coupling points.The transformation for Fano resonance effect and electromagnetically induced transparency(EIT)effect is achieved by controlling the resonant mode.The multiple resonant modes are finely tuned by choosing the bump structure in the microcapillary.The Fano resonance lineshapes with different phase is achieved,and the Fano resonance effect and EIT effect is simultaneously adjusted.The multiple mode coupling effect not only can be applied to improve sensing performance and improving nonlinear optical effects,but also pave a way for multi-channel optical switching devices,multi-channel optical communications and multi-channel information processings.(4)The non-linear optical effects in ultra-high-Q factor silica microresonator are systematically studied.The non-linear optical effects in the microbottle,including stimulated Raman scattering(SRS),stimulated Brillouin scattering(SBS),and four-wave mixing(FWM)effect,are excited.The stable optical frequency comb is achieved based on the interaction of multiple mechanisms.Firstly,the characteristic of low power threshold of the non-linear optical effects is demonstrated.The SRS with narrow bandwidth,high gain,and high signal to noise ratio is obtained.The Raman laser can be tuned by changing the environment temperature.The sensibility of temperature tuning is about 13.59 pm/?.Secondly,the frequency shifting values of the first order SBS and the second order SBS are 11.03 GHz and 22.07 GHz.The result will push the way of microwave source.Finally,the FWM effect with different wavelength expansion for two modes is obtained.The wavelength range optical frequency comb up to 250 nm is achieved.Besides,the broadened SRS and SBS based on FWM effect is observed.These multi-wavelength laser source prove its potential in precision range and spectroscopy measurement,gas detection based on the characteristics of molecular spectra and biosensors.(5)The non-linear optical effects in ultra-high-Q factor calcium fluoride crystalline microresonator are systematically studied.The non-linear optical effects in the microbottle,including stimulated Raman scattering(SRS),stimulated Brillouin scattering(SBS),and four-wave mixing(FWM)effect,are excited.Clean SRS based on FWM effect is obtained by processing fine structure on the azimuth direction.To fabricate such resonators,we develop a home-made machining system.The shape of the microresonators fabricated is a spheroid.The relationships between Q factors and processing,surface roughness,and external couping are analyzed.With our home-made machining system,the surface of the rim of the structure are engineered to be low to 1 nm.The disk-taper coupling system exhibits an ultra-high-Q factor up to?108.More importantly,a customized packaged structure for our crystalline resonator is proposed.The packaged structure can be integrated in all types of optical electronic devices.Several nonlinear optical effects in the stable packaged structure are demonstrated.The power threshold of the first order SBS is about 49 mW and the power threshold of the second order SBS is about 102.6 mW.Their frequency shifting values are 12.01 GHz and 24.02 GHz.The SNR of the first order SBS reaches 36.2 dB.Furthermore,the multi-mode Raman-FWM effect is observed.These low power threshold non-linear optical effects in the stable packaged structure greatly extend the frequency range of the laser and can be applied in various applications,such as optical communications,biosensor and environmental monitoring,laser science,spectral analysis,and microwave source. |
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