Sensing Research Of Whispering Gallery Modes Microcavity Based On Liquid Crystal

Whispering gallery mode(WGM)optical microcavity has been studied by a large number of scholars for its high sensitivity sensor,low threshold laser and optical communication device due to its extremely high quality factor(Q)and minimal mode volume.Other fields have shown great potential for application,among which the research application in the sensor field is the most mature.Liquid crystal(LC)is a highly advantageous optical material due to its good temperature and electric field response and surface anchor orientation.Therefore,the study of LC as a WGM optical microcavity has made it possible to implement various types of high sensitivity sensor devices.In this paper,the application of liquid crystal as WGM microcavity in temperature,electric field and biochemical molecular sensing is studied.The WGM resonance characteristics of dye-doped liquid crystal microsphere laser excitation are discussed.By monitoring the WGM spectral resonance peak displacement,temperature,electric field and myricetin sensing are realized.The main research contents are as follows:(1)A liquid crystal microsphere cavity is obtained by filling a liquid crystal in a hollow glass spherical shell coated with a polydimethylsiloxane(PDMS)film using a tapered capillary microtube syringe prepared by a flame heating taper.It was found by POM photo observation that the liquid crystal microspheres under the action of PDMS film had a radial structure,and the WGM laser emission threshold obtained under 532 nm pulsed laser excitation was lower.Then the WGM emission spectrum of liquid crystal microspheres was analyzed,and the quality factor and resonance mode were calculated.The variation of laser emission FSR value and liquid crystal microsphere size was given.The results show that the FSR value is inversely proportional to the diameter of the microspheres.The liquid crystal microspheres in such glass spherical shell are used for temperature and electric field sensing.For temperature sensing,the response of WGM laser resonant wavelength ? to temperature is measured by theoretical calculation and experimental calculation,and its value decreases linearly with temperature increase.The calculated and measured temperature sensitivity are 0.852nm/? and 1.029nm/?,respectively.The value is basically the same and the sensitivity is higher than other types of WGM microcavity temperature sensors;for electric field sensing,the microsphere structure transition caused by the orientation deflection of liquid crystal molecules under the electric field is analyzed first,and then monitored.The WGM spectral change closely related to the internal structure of the microspheres,in the process of increasing the applied voltage from 0.3V/?m to 0.65V/?m,the obtained liquid crystal microsphere WGM laser resonance wavelength ? produces a total of 2.28nm blue shift.This solid-coated liquid crystal microsphere,which can simultaneously realize temperature and electric field sensing,is more suitable for detection in various complicated environments due to its stability.(2)Further,the liquid crystal microspheres were used for biochemical molecular sensing,and the detection of myricetin was studied.Liquid crystal microspheres were prepared by surface tension in a water-phase environment using a conical capillary syringe.POM photos of liquid crystal microspheres were obtained after adding DTAB,DNA and myricetin solution in an aqueous environment.The internal structural changes are constantly changing between bipolar and radial.Subsequently,the interference term was excluded,the feasibility of myricetin sensing was initially confirmed,and the influence of various metal ions on the experiment was discussed.By comparing the effect of metal ions on DTAB and myricetin,it explains why metal ions can not be observed to promote the degradation of myricetin.Finally,the 532 nm laser excited liquid crystal microspheres,and the WGM excitation spectra were obtained under different concentrations of myricetin.The spectral shifts were analyzed.The results show that the structural changes of the liquid crystal microspheres reflected by WGM spectra are consistent with those observed by POM photos.In the range of 31.6?M to 54.5?M,the WGM resonance peak produced a blue shift of 0.89nm with a sensitivity of 0.04nm/?M.The minimum concentration interval of myricetin detectable by this method was estimated to be 0.3 ?M.This accurate quantitative measurement of myricetin can be achieved by monitoring the sensing mode of the WGM spectral changes of the liquid crystal microspheres.