Theoretical Study On Biosensing Characteristics Of Photonic Crystal Ring Cavity Based On PSO Algorithom

The biological sensing technology is a product of the combination of life scienceand information science，which is very active in engineering research field. Photoniccrystal Label-free biosensor is detected in the natural state of biological samplessensor using optical means, high sensitivity, compact structure, no electromagneticinterference, easy integration, real-time monitoring, which plays a unique advantage inthe aspects of interaction analysis on the low concentrations of bimolecular and lowaffinity bimolecular. The resonant cavity and waveguide are the basic structure ofphotonic crystal, and the coupling structure composed of photonic crystal resonantcavity and waveguide has been widely applied in the field of sensor technology. Basedon the coupling characteristics and the theoretical model, the paper designs andoptimizes the ring cavity structure theoretically, and discusses its application in thebiosensor field. The main contents of this thesis are as follows:First, according to the basic electromagnetic field theory, we analyzed thephotonic band-gap properties of the complete photonic crystals and photonic crystalswith defects using the plane wave expansion method. And we analyzed thetransmission properties of the coupling structure constituted with photonic crystalsresonant cavity and waveguide. Then the photonic crystal ring resonant cavitystructure and parameters that are suitable for analysis of the filtering and sensingproperties can be obtained.Next, based on numerical calculation method of the photonic crystal, we optimizethe parameter of photonic crystal ring resonant cavity structure by using particleswarm optimization algorithm and Finite Difference Time Domain method (FDTD).Take the maximal normalized transmission rate for optimizing object function,according to the position-velocity updating formula of the PSO method, the radius ofscattering air holes, coupling air holes and internal air holes of the photonic crystaldefect were optimized globally, and then we found the optimal sizes.Finally, the sensing property has been analyzed using the sensor structureoptimized, in which the coupling area and the inner area have been adopted as the sensing region respectively. The simulation results have shown that the shift of theresonant wavelength has the linear relationship with the change of the refractive indexfor the biological sample, in which the refractive index biosensor can provide effectiveguidance for the detection of the refractive index for the biological sample.