High sensitivity refractive index sensor based on micro-fiber with micro-arched transition

摘要

A novel refractive index (RI) sensor based on micro-fiber with micro-arched transition (MMAT) was proposed. The power extinction ratio of interference spectra was enhanced by the micro-arched transition. Although the waist diameter of micro-fiber was less than 6 mu m, the power extinction ratio was larger than 10 dB, which was critical to the spectral dip measurement. The relationship between waist diameter of micro-fiber and RI sensitivity was systematically investigated. It turned out that higher RI sensitivity of MMAT could be obtained by decreasing the waist diameter of micro-fiber. While the waist diameter was 5.6 mu m the RI sensitivities of MMATs were up to 2739.8 nm/RIU, 4515.7 nm/RIU and 12,620.0 nm/RIU in the RI range of 1.333-1.3580, 1.3705-1.3905 and 1.3940-1.3980 respectively. The sensor was applied to detecting the concentrations of bovine serum albumin (BSA) solutions and showed the sensitivity of 0.3 nm/(mg/ml). Owing to its small volume and high sensitivity, this kind of senor can be expected to widely apply in fields of biology, chemistry and physics.