Study On Sensing Characteristics Of Photonic Crystal Based On Surface Defect Cavity With Porous Silicon

It is a comparatively novel subject to investigate photonic crystal. The optical biosensor designed based on photonic crystal with characteristics of small size and high detection sensitivity, has become a hot issue in research of optical biosensor and opened a new chapter for optical sensing technology. Therefore, started from the characteristics of photonic crystal and based on the study of surface wave theory, a new refractive index sensor structure model based on photonic crystal structure containing surface defect with porous silicon has been proposed, and its sensing characteristics are studied by the Goos-H?nchen shift, then its properties are analyzed, which provides theoretical support for the research of photonic crystal biosensor. The research contents are mainly included as follows:Firstly, based on the surface wave resonance principle of semi-infinite photonic crystal containing surface defect and porous silicon optical properties, the photonic crystal sensor structure model is proposed, in which the defect cavity on the surface is established by introducing the porous silicon layer and the absorbing medium layer,and the sensing region of the sample detected is formed by the use of the efficient carrying mechanism of the porous silicon. The existence of surface wave has been demonstrated at the edge between the defect cavity and the periodical photonic crystal structure, and the total reflection in the defect cavity has been formed by adjusting the incident angle. The resonant defect peak has been obtained in the reflection spectrum by adding an absorbing media in the defect cavity in order to decrease the reflectivity of the resonant wavelength.Secondly, according to the relationship between Goos-H?nchen phase shift and the resonant wavelength, the relationship model between the resonant wavelength and the effective refractive index variation of porous silicon adsorbing layer caused by the change of the refractive index of the sample has been established, and its refractive index sensing characteristics have been analyzed. Based on those results, The full width at half maximum and the quality factor can be optimized by adjusting the parameters of photonic crystal. In order to improve the sensitivity of the sensor, the BP neural network is adopted to optimize the thickness of porous silicon globally.Finally, the sensing characteristics of the photonic crystal sensor structure is analyzed.The different spectral characteristics when porous silicon is filled with gas or liquid respectively are studied, which can demonstrate the effectiveness of the structure. The structure provides some theoretical references for the design of refractive index sensors with high Q value and sensitivity and displays the design and application potential in optical sensing.