Structural Design And Performance Of Binary Metal-grating-based Surface Plasmon Resonance Sensor

In order to improve the performance of binary metal-grating-based surface plasmon resonance(SPR) sensor, and realize the SPR mode splitting at infrared wavelength band, based on the experience in the past, the SPR sensing characteristics and optic properties are investigated in the thesis.The main research works and conclusions are as followings:(1) Using the Finite Difference Time Domain(FDTD) method, the structure parameters of wavelength-sensitive grating based SPR sensor are optimized. By studying the influence of structure parameters on the reflection characteristic curve, we find that the “substrate peak” will be completely eliminated when the thickness of metal substrate film d?100 nm. And the changes of grating width and depth not only correct the position of resonance wavelength, but also significantly modulate the minimum reflectance at resonance(MRR) and the full width at the half maximum(FWHM). The optimized grating structure parameters are: p=1530 nm,w=1200 nm,h=25 nm,d=100 nm, the corresponding sensitivity is 1540 nm/RIU and the figure-of-merit(FOM) is 1442.2.(2) Using the rigorous coupled wave analysis(RCWA) method, the structure parameters of angle-sensitive grating based SPR sensor are optimized and the influence of grating metal(Al) oxidization to the sensor performance is analyzed. We present the wavelength(?)-independent ultimate angular sensitivity of a SPR sensor, as long as the grating of metal has much higher permittivity than analyte(na2). For 1.32?na?1.36, real sensitivity of optimized SPR sensor increases from 292.5(344.5) to 338.0(396.3) ?/RIU at respective ?=0.85 and 1.55 ?m by the single(double)-dip method. After the metal oxidization, the sensitivity is degraded by ?3.2%(2.8%), and the detection error of ?na?1.3e-3(1.1e-3) is introduced to the sensor working at near-infrared wavelengths of interest. Therefore, the metal oxidation effect can be ignored by reason of the tiny changes of the sensor performance.(3) The thesis presents a new composite structure grating, which is consisted of double metal gratings; meanwhile, the gas sensing performance is studied. Split modes of SPR in composite metal grating are observed by the FDTD method. The original structure symmetry is broken and changed with the increase of relative displacement between the double gratings; as the result, the resonant modes move in an opposite direction. When the relative displacement is further increased till to the double gratings connected to form a new symmetrical single grating, the separate resonant modes will reconsolidate to another single resonant mode. When the refractive index of analyte is 1.01?na?1.05 and the relative displacement of double gratings is zero, the wavelength sensitivity of composite metal grating gas sensor reaches 1207.5 nm/RIU(per refractive index of unit) and the FOM is 1290.7; while the relative displacement of the double gratings is 100 nm, for the double split modes the wavelength sensitivities are 1205.0 and 1210.0 nm/RIU, respectively, and the corresponding FOMs are 1295.4 and 762.3.