Fiber cladding SPR sensor based on V-groove structure

The difficulty with fiber cladding Surface Plasmon Resonance (SPR) sensors lies in coupling the core mode to the cladding mode without removing the cladding. This paper hereby endeavors to demonstrate a fiber cladding SPR sensor based on V-grooves structure by using a CO2 laser. V-grooves are engraved on single-mode fiber, step-index multimode fiber, and graded-index multimode fiber. When the transmitted light reaches the V-grooves structure, the higher-order cladding mode is excited, and a metal film is coated on the 2 cm cladding area after the V-grooves to form fiber cladding SPR sensors. This paper investigates the refractive index and bending sensing of V-groove cladding SPR sensors of single-mode, graded-index multimode, and step-index multimode fibers. The experimental results show that: the refractive index sensitivity of three kinds of sensors is 2811.34 nm/RIU, 1862.33 nm/RIU, and 1418.85 nm/RIU, respectively, and the curvature sensitivity of three types of sensors is 0.42 nm/m−1, 1.03 nm/m−1, and −6.59 nm/m−1, respectively. The proposed sensors in this paper are easy to manufacture, demonstrate quality of high sensitivity, and can be applied extensively.