| WGM microresonators have attracted great interests of research scholars in various fields due to the significantly enhanced light-matter interactions originating from their ultra-high quality?Q?factors and small mode volumes,which have exhibited enormous potential in the fields of lasing,sensing,biological detection,nonlinear optics and quantum physics.Microresonators-based sensors,as the most representative and important branch in the application research of microresonators,have aroused extensive attention in recent years,while the improvement of sensitivity is becoming a key breakthrough point of its further development.Liquid crystal?LC?is an important player in the field of display,because of its unique birefringence characteristics and good electromagnetic and temperature responses.LC microdroplets WGM resonator combines the advantages of both,and it not only possesses the advantages of simple manufacture,flexible operation and good costing but also has the potential of improving the sensing sensitivity.This thesis explores a series of experimental studies on the sensing properties of the LC microdroplets WGM resonators,verifies the WGM resonant properties in the different kinds of LC microdroplets and realizes the microdroplet-based highly sensitive temperature sensing.The detailed research contents are given as follows:?1?With the flame heated taper-drawing technique,the tapered capillary microtube was prepared,which was used to generate the dye-doped cholesteric liquid crystal?DDCLC?microdroplets in the aqueous environment with low refractive index.Under the excitation of532nm pulse lasing,we observed the typical WGM lasing emission in the DDCLC microdroplet,and the lasing threshold was about 0.9?J.We verified the WGM nature in the CLC microdroplet from the theoretical simulations and experiments two aspects.On the one hand,we established the FDTD simulation model of the CLC microdroplet and the results verified the WGM resonant action of light propagation in the microdroplet.On the other hand,we experimentally studied the influences of microdroplets sizes on the lasing wavelengths,FSR and Q.The experimental results shown that the variation of all parameters with microdroplet sizes is in according with the WGM resonant properties.In addition,we desighed and conducted a temperature sensing experiment of the CLC microdroplet.The sensing sensitivity was up to-1.5nm/?,and the temperature resolution was 2.73×10-2?.?2?By coupling the nematic liquid crystal?NLC?microdroplet with the evanescent wave generated from the tapered fiber waveguide,the WGM peaks of the NLC microdroplet was abserved in the transmission spectrum,and the Q of the resonant mode was about 2.8×103.We experimentally observed the spectral modes splitting induced by the natural deformation of microdroplet,which was attributed to the lifting of the azimuthal mode degeneracy.We investigated the influences of the taper-microdropelt distance on the coupling states,and the results shown that the coupling states were under-coupled,critically coupled and over-coupled,respectively,with the decreased of coupling distance.In addition,we conducted a temperature sensing experiment of the NLC microdroplet.The sensing sensitivity was-267.6pm/?,and the temperature resolution was 7.5×10-2?. |
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