▎ 摘　　要

A refractometer that integrates graphene oxide (GO) with the polarization maintaining microfiber (PMMF) has been proposed and experimentally demonstrated for measuring the refractive index (RI). It is based on the effective birefringence a highly sensitive response to the external RI variation in the Lyot interferometer when the principal axes of the tapered and untapered sections are orthogonal in the PMMF. In addition, the response mechanism of effective birefringence is theoretically simulated and analyzed to investigate the influence of the taper waist diameter on it. The experimental results show that the RI sensitivity of the PMMF refractometer is 4025.0 nm/RIU in the RI range of 1.3333 similar to 1.3457 when the waist diameter is 54 mu m. By reducing the waist diameter to 28 mu m, the RI sensitivity reaches as high as 11043.6 nm/RIU. It is attributed to alleviating the adverse impact of the inherent birefringence of the PMMF on its response to the ambient RI. With the GO affixed on the PMMF with waist diameter of 28 mu m using chemical bonding and physical adsorption deposition technology, the linear RI sensitivity is further enhanced to 12251.6 nm/RIU. This is due to the hydration and increase in the specific surface area of PMMF caused by GO. The proposed GO-PMMF refractometer features linear and high RI sensitivity, relative robustness, simple construction, and reproducibility. It has immense potential for future improvement of biosensing.