Research On Biosensor Based On The Periodic Metal Grating

The multilayer and plasmon sensors are more and more widely used in practical applications.However,some sensor structures based on multilayer and plasmon are complex in design,and must use the prism coupling,wedge coupling and fiber coupling so that the interaction of light and sensors to work properly.These traditional coupling methods increase the size of the device and the difficulty of the preparation,but also makes the detection process very complex,and bring a lot of inconvenience to the practical applications.In order to solve these problems,the grating structure based on multilayer and the structure of silver grating based on PMMA are designed.The theoretical simulation and experimental verification of the sensitivity of the grating structure to the external environment are carried out comprehensively.Aiming at the problem of increasing the size and sensor instability of the traditional coupler,a gold grating sensor based on Ti O2/Si O2 multilayer was designed and simulated by the COMSOL software.At the TE and TM polarization,the different order waveguides mode can be achieved in the multilayer.The experimental results and simulation results are very consistent.Compared with other resonances,this coupling method is easy to achieve and is not affected by the external environment.Not only to achieve the purpose of reducing the size of the device,but also to increase the anti-interference ability of the structure to the external environment.After designing the structure which is insensitive to the external environment,aiming at the problem that the biosensor structure design is complex and the local surface plasmon(LSP)dark mode is difficult to be excited,two kinds of structures which are sensitive to external environment based on the PMMA grating are designed.One is the metal-covered PMMA grating with continuous silver sidewalls,the other is the metal-covered PMMA grating without sidewalls.The quadrupole dark mode of LSP is present in the grating with sidewalls.The preparation of the sidewall of the grating is realized by improving the coating process.The experimentally measured reflective index sensitivity is around458 nm/RIU(refractive index unit).The sensitivity of the dark mode to the external environment was 1.5 times the sensitivity of the bright mode.The simulation results are in good agreement with the simulation results.The microfluidic channel and the sample sealing process were developed to realize the detection of bovine serum albumin biomolecules.The sensitivity of the PMMA grating with sidewalls to the biomolecule detection is about 6 times of the PMMA grating without sidewall.The designed structure achieves the purpose of reducing the size of the device and the application in the sensor.The gold grating structure based on the multilayer has successfully realized the coupling of the light,which is very insensitive to theenvironmental change.In the future,this structure has the application value of improving the photodetector sensing performance.At the same time,the design of silver grating structure based on the PMMA successfully realized the dark mode excitation.These silver grating structures have high sensitivity to the external environment change,and realized the application in biomolecule detection.