Investigation of Intra-Cavity SPR Sensor Based on Erbium-Doped Fiber Laser

In this paper, an intra-cavity SPR sensor based on erbium-doped fiber (EDF) laser is proposed to achieve higher sensitivity for detecting analyte refractive indices. A liquid-core fiber-based SPR sensor is first designed to match the operating wavelength of 1530 nm in the fiber laser intra-cavity, and then placed into the cavity of the EDF laser to constitute the all-fiber intra-cavity SPR sensor. We theoretical investigate the influence of pump power, cavity loss and EDF length on the sensitivity of the proposed intra-cavity SPR sensor. The results indicate that the sensitivity of the intra-cavity SPR sensor can reach 1.051 × 10 ⁹ RIU ⁻¹ (refractive index unit), which is enhanced 4 × 10 ⁶ times compared with the sensitivity of 253 RIU ⁻¹ obtained by the SPR sensor without fiber laser cavity. In addition, the sensitivity of the proposed intra-cavity SPR sensor can be flexibly tuned by changing pump power, cavity loss or EDF length. This work demonstrates that as an alternative approach, the combination of the fiber laser intra-cavity spectroscopy and the fiber-based SPR sensor can achieve a remarkable enhancement in sensitivity.