Infrared plasmonic refractive index sensor utilizing 2D grating of nano-bowtie particles for both gas and liquid

Abstract We propose a plasmonic structure that can be used for refractive index sensing with different analytes in the same wavelength-domain. A two-dimensional (2D) grating composed of nano-bowtie particles is used as the optical momentum coupling structure. The double-period feature of the 2D grating makes the structure have two excitation approaches with different polarization directions of incident light. The physical mechanisms of the plasmonic structure are revealed in detail by theoretical analysis and finite-difference time-domain method. The simulation results show that the structure can achieve a gas sensing sensitivity of 1235 nm/RIU and a liquid sensing sensitivity of 950 nm/RIU in the same wavelength-domain from 1200 nm to 1400 nm. This structure can be widely used in the field of gas or liquid biochemistry due to its simple geometry and competitive sensing performance.