[5a-A410-1~8] 4.1 Plasmonics

▲ [5a-A410-8] Refractive Index Sensor based on Multilayered Au-SiO₂-Al Structure

〇ASHISH BIJALWAN¹, VIPUL RASTOGI¹ (1.Department of Physics, Indian Institute of Technology Roorkee, Uttarakhand, India 247 667)

Keywords:Surface Plasmons, Metallic grating, Multilayer Structure

We present a multilayered Au-SiO₂-Al structure assisted surface plasmon resonance (SPR) based refractive index sensor. The performance of the sensor has been evaluated on the basis of sensitivity and FWHM. Rigorous coupled wave analysis (RCWA) was used to carry out the numerical simulations. Our study shows that the sensitivity of conventional gold grating (grating engraved in gold) based SPR sensor is about 184°/RIU with FWHM of 1.675°. To improve the performance of the sensor, we introduced an aluminum layer underneath gold grating. This bimetallic structure offers sensitivity of 196.5°/RIU with reduced FWHM (< 0.525°). We observed that aluminum could improve the performance of the sensor but it undergoes oxidation if exposed to air and it may affect the performance of the sensor. To prevent the oxidation of the aluminum, we proposed a new configuration. It consists of an SiO₂ layer sandwiched between gold grating and aluminum film. We found that sensitivity of the proposed structure is 191.9°/RIU with FWHM less than 0.96°. Thus, we could enhance the sensitivity of the conventional gold grating based sensor with reduced FWHM using Au-SiO₂-Al based structure. Proposed multilayered structure could reduce the FWHM at least by 44 % and hence could improve the resolution of the sensor.