Study On Sensing Characteristics Of Surface Coated Waveguide Grating With Porous Silicon Layer

In recent years,with the gradual maturation of waveguide grating theory,waveguide grating has become the focus of researchers due to its unique resonant characteristic,and it is widely used in various fields of optical sensing.In this paper,a waveguide grating sensing structure with porous silicon layer is proposed based on the principle of waveguide grating resonance and the unique optical sensing mechanism of porous silicon,the resonant spectral characteristics are optimized by coating the polymer functional film on the grating,the refractive index sensing mechanism is established based on the resonance conditions and the Goos-H?nchen theory,and the refractive index sensing characteristics are also analyzed,the main works are as follows:Firstly,based on the diffraction characteristics of grating and optical characteristics of dielectric waveguide,the resonance principle and resonance forming conditions of waveguide grating are analyzed.The equivalent waveguide model of waveguide grating is analyzed based on equivalent medium theory.According to the resonant Eigen equations of waveguide grating,the effects of grating parameters,waveguide parameters,substrate parameters,cladding parameters and incident angles on the resonant spectra of waveguide grating are analyzed.The results provide theoretical guidance for the research of waveguide grating sensors.Secondly,based on the principle of waveguide grating resonance and the optical sensing mechanism of porous silicon,a waveguide grating sensor with porous silicon sensing unit is proposed.The resonance wavelength and the refractive index of the samples are established based on the resonant phase conditions,the waveguide grating material is optimized and selected according to the influence rule of the waveguide grating parameters on the resonant spectrum,and the refractive index sensing characteristics of the sensing structure are analyzed.Finally,a surface coated waveguide grating sensor with porous silicon layer is proposed,the resonant spectrum of the grating is optimized by coating the polymerfunctional layer on the grating,and the Q value and sensitivity are improved.The sensing characteristic was analyzed by establishing a mathematical model between the resonant wavelength and the refractive index of the sample,the sensing structure shows better detection performance than before the coating.