Structural Design And Sensing Performance Optimization Of Biosensor Based On Flexible Optical Resonator

In recent years,with the development of biomedicine,environmental sciences,life sciences,and other fields,the demand for biomolecule detection by researchers is increasing,and the demand for high-precision and high-sensitivity biosensors has become increasingly urgent.Since the optical biosensor based on the whispering gallery mode microcavity has the advantages of high-quality factor,high sensitivity,high integration,etc.,it has been paid more and more attention by researchers.If the traditional whispering gallery mode microcavity can be combined with the emerging deformable flexible structure,it can break through the inherent mechanical constraints of rigid devices,thereby expanding its application prospects in internal/external detection,skin sensing,and other aspects.However,when this kind of flexible photonic device is mechanically deformed under the action of external pressure,under the influence of the strain-optical coupling effect,the geometric size of the device and its effective refractive index will change accordingly,causing the resonance wavelength to shift,thereby affecting biosensing results.High mechanical flexibility is difficult to be compatible with high biosensing performance,making it difficult for flexible photonic devices to be widely used as biosensors.Therefore,to expand the application range of flexible photonics in biosensing,it is necessary to design a novel flexible optical microcavity structure based on ensuring the compatibility of high flexibility and high sensitivity.This thesis first analyzes the strain-optical coupling effect and its influence of the flexible whispering gallery mode microcavity in the process of biosensing.On this basis,two novel structures are proposed to eliminate the interference caused by the strain-optical coupling effect,to achieve high flexibility and high sensitivity mutual compatibility.Firstly,from the perspective of multi-parameter sensing,a dual-parameter sensor based on a dual-polarization microring resonator that can measure the refractive index and pressure at the same time is proposed.By simulating the structure of the dual-polarized microring resonator under different external conditions,the refractive index and pressure sensitivity corresponding to the two polarization modes were calculated.By calculating the inverse matrix of the second-order sensitivity matrix,the resonance wavelength shift caused by biotic and abiotic factors can be distinguished,thus the interference caused by the strain-optical coupling effect can be eliminated.Secondly,from the perspective of reducing the strain distribution near the device structure,a novel flexible pedestal microdisk resonator structure that can realize biosensing is proposed.The strain is reduced by introducing a pedestal structure between the substrate and the microdisk resonator.Through the analysis of the strain and the optical performance of the novel structure,it is found the sensing performance of the novel flexible pedestal microdisk resonator is twice that of the traditional resonator.In addition,the influence of the pedestal structure on the strain of the device is also studied.It is found that by changing the pedestal structure,the strain near the device structure can be minimized to 10-6 με,In this case,the resonant wavelength shift caused by the strain-optical coupling effect is only 10-6-10-5 pm,which is completely negligible compared with the resonant wavelength caused by biological factors.From the perspective of device structure design,this thesis provides a new path for realizing optical biosensors with high mechanical flexibility and high sensitivity.