Design and study of highly negative sensitive mid-infrared surface plasmon resonance sensor based on microstructured fiber for high refractive index sensing

A new surface plasmon resonance (SPR) sensor is proposed that uses a microstructured fiber (MF) with a simple structure to detect high refractive index (RI) within the mid-infrared region. Numerical analysis of the sensing properties has been conducted by using a full-vector finite element method, and the simulation findings reveal that the proposed sensor can achieve single-resonance negative RI sensing within the mid-infrared wavelength range of 2.503-2.8 mu m when the RI of the analyte varies from 1.50 to 1.52. By optimizing the structure of the sensor, the maximal negative wavelength sensitivity of 15700 nm/RIU and a high amplitude sensitivity of 111 RIU-1 are achieved. In addition, the negative RI resolution is as high as -6.37x10(-6) RIU when the instrument's resolution is 0.1 nm. Therefore, our proposed sensor has a lot of potential for high RI sensing, including the detection of highly active chemical and biological liquid samples.