Research On Particle Counting And Sensing Of Liquid Core Microcavity

Whispering gallery mode(WGM)microcavity has the characteristics of high Q value and small mode volume,which make it has a good application potential in sensing.At present,due to the limited interaction between light and matter caused by low order modes,the detection of larger(>1?m)particles cannot be realized in the microcavity.However,the high order resonant mode of liquid core microcavity is more suitable as a platform for the interaction of light and matter due to its advantages of larger energy ratio of liquid core,deeper penetration depth and stronger interaction between light and matter.Therefore,we will study the application of the liquid core microcavity in particle counting and sensing.In this paper,a method of particle counting based on the optical pulse generated by the microcavity resonance is proposed,and the particle counting based on liquid core microcavity is studied.We use a thin fiber taper to excite the liquid core capillary microcavity to generate high order Fano resonance with high sensitivity.When the particles(PS microspheres or SAP broken beads)pass through the whispering gallery mode,the interaction of light and matter causes a shift in the Fano resonance spectrum,which modulates the continuous incident light of fixed wavelength into pulse light.Similar to the Coulter electric pulse or scattered light pulse,this resonant optical pulse can also realize particle counting.In addition,the reason for the specific shape of the optical pulse is analyzed.The feasibility of the method is verified by theory and experiment.Finally,according to the characteristics of the spectrum,the criterion of how to identify the target particles is put forward to facilitate the counting.The counting method proposed in this paper does not need complex circuits or optical devices,and it is stable and efficient.It can count particles with different refractive index effectively,and has a very good application prospect in particle detection.In addition,the liquid core microcavity can also be used as a high sensitivity temperature sensor and liquid flow rate sensor.First of all,the ultra-thin fiber taper is used to excite the high order Fano resonance in the liquid core microcavity,and ethanol with a high thermo-optical coefficient is used as the liquid core material to realize high sensitivity temperature sensing.The temperature sensor can realize high sensitivity temperature sensing with a sensitivity of-0.402nm/? and detection limit of 0.026?.Based on this temperature sensing theory,the liquid flow rate sensing can be further realized.In the experiment,the microcapillary is also used as the liquid core microcavity,and an injection pump is utilized to change the liquid flow rate,so a segmented flow velocity sensing is realized.When the flow rate is low,the mode blue shift area is used for sensing and the maximum sensitivity is-0.045 nm per ?L/min;when the flow rate is high,the mode red shift area is used for sensing and the maximum sensitivity is 0.013 nm per ?L/min.