Structural Design And Performance Optimization Based On Flexible Optical Microring Resonator Biosensor

With the increasing demand for medical diagnosis,environmental protection,and in situ monitoring for biochemical and physical parameters,integrated photonics has gradually penetrated major emerging application fields.Among them,the whispering gallery mode(WGM)optical micro-resonators have shown significant attraction due to their high quality factor,low mode volume,strong anti-interference ability,and compactness.If WGM optical resonant cavities are combined with flexible devices with mechanical deformation ability,high-sensitivity biosensors application that fits the curved surface environment of human skin can be realized,and they show excellent application prospects for life sciences,biomedicine,and other fields.However,when flexible photonic devices are bent under pressures,the size of WGM optical resonant cavities and the refractive index of the material will be changed due to the shear stress and the strain-optical coupling effect,which will cause the resonant wavelength shift in the transmission spectrum.As a result,the detection process is mixed with nonbiological factors,and the accuracy of the biological detection results is seriously reduced.Therefore,it is necessary to study a new sensing mechanism or new structure to eliminate the stress near WGM optical resonant cavities and effectively control the strain-optical coupling effect,so that flexible WGM optical resonant cavities can accurately and sensitively acquire biosensing information and truly realize biological sensing.This essay firstly proposes a new flexible microring resonator structure based on the serpentine waveguide island bridge structure to reduce the stress near the cavity.The mechanical effects of the structure under both stretching and bending states are analyzed through three-dimensional finite element simulation.it is proved that this structure has a significant optimization effect in weakening the internal strain of the device.In addition,through three-dimensional finite difference time domain simulation,the refractive index biosensing performance of the structure under two mechanical deformations is analyzed.The simulation results show that this new type of flexible microring resonator not only has good stretchability and bending flexibility,but also has excellent biosensing performance.Secondly,from the perspective of eliminating the influence of the strain-optical coupling effect on the resonance wavelength,a concentric ring single-opening resonant cavity structure based on a flexible substrate is proposed.Through three-dimensional numerical simulation,the transmission spectrum of the resonant cavity under different refractive indexes and under different pressures can be obtained.And then the pressure sensitivity and refractive index sensitivity corresponding to symmetric standing wave mode and asymmetric standing wave mode are calculated.Therefore,the second-order sensitivity matrix is established,and the change of the single factor in environmental refractive index and pressure can be measured simultaneously by solving the inverse matrix of the sensitivity matrix,thereby completely eliminating the influence of the strain-optical coupling effect in the field of biosensing application.In this paper,the research on flexible WGM optical resonant cavities lays the foundation for its application in flexible photonic integration and provides a new way to realize high-sensitivity flexible optical biosensors.