Refractive index sensing and filtering characteristics of side-polished and gold-coated photonic crystal fiber with a offset core.

• A side-polished gold-coated photonic crystal fiber with a offset core is proposed. • The U-shaped air hole arrangement can enhance the leakage of the evanescent field. • The PCF integrates RI sensing and polarization filtering. • The maximum sensitivity within the RI range of 1.35–1.39 is 12,500 nm/RIU. • The proposed PCF polarization filter has bandwidth tunability. The transmission characteristics of a side-polished eccentric photonic crystal fiber (PCF) is studied by using the full-vector finite element method (FV-FEM). The proposed structure is composed of air holes similar to a U-shaped arrangement, and there is a small air hole between the side polishing plane and the core region to enhance the leakage of the evanescent field in the y polarization direction. It integrates refractive index (RI) sensing and polarization filtering. The RI sensing mainly works in the visible light band, while polarization filtering is suitable for the near-infrared band. The maximum sensitivity of the sensor is 12,500 nm/RIU, and the resolution is 8.0 × 10−6 RIU in the detection RI range of 1.35–1.39. By changing the external RI or the thickness of the gold-coated film, the bandwidth-tunable PCF polarization filter with excellent performance can be obtained. Therefore, the design of side-polished PCF will be of great significance to the development of integration and miniaturization of optical devices. [ABSTRACT FROM AUTHOR]