Investigation Of Whispering Gallery Modes Splitting And Microfluidic Sensors

Whispering gallery mode(WGM)optical microcavity can greatly enhance the interaction between light and matter due to its extremely high quality factor(Q)and microscale mode volumes.Spherically optical resonators have garnered a great deal of research attention owing to their high quality factors(Q)and microscale mode volumes,which are beneficial informative in regards to underlying physics and potential optical applications including laser sources,optical filters,and biological sensors.In recent years,microfluidic sensors based on WGM multi-cavity coupling and solid-state microcavity WGM have attracted wide attention.The specific research contents include:(1)Mode splitting behavior between pairs of size-matched microspheres with tight-binding positions was observed.Two coupled microspheres were excited via a conical fiber tip positioned in parallel or perpendicular configuration.The conical fiber tip-bisphere coupled system of the perpendicular configuration was more efficient for the numerical simulations and experimental results.We demonstrate the effects of spacing between two coupled microspheres on the mode splitting spectra,and mode splitting was decreased with increased spacing between the microspheres.Furthermore,we also performed temperature-dependent experiments to find out the dip wavelengths induced by mode splitting which can be tuned by controlling temperature.A range of 0.6 nm variation was achieved within 20 °C in the bisphere system.Meanwhile,coupling strength(WGM splitting)overall remains steady in comparatively higher temperature range.(2)Using PDMS-made microfluidic channels,the dye-doped polystyrene microspheres were fixed in the channels and the lens-focusing method was used to focus the pump light through the lens onto the surface of the microfluidic chip.The pump light through the chip,and to the microfluidic chip finally.The typical whispering gallery mode laser was observed.By injecting different refractive index liquids,the resonant wavelength changes,the results showed that microfluidic sensor sensitivity was about 310 nm/RIU.Furthermore,the repeatability of the microfluidic sensor was also measured.In the cyclic refractive index measurement experiment,the laser wavelength changes linearly with the refractive index of the liquid,and the relative difference in temperature sensitivity obtained by two experimentsof rising and falling is only 0.33%.Meanwhile,we use the experimental principle that penicillinase can accelerate the hydrolysis of penicillin and change the refractive index of the liquid environment,real-time monitoring of the refractive index change of the mixed liquid is realized on the Y-shaped channel microfluidic sensor.