High-Sensitivity and Direction Recognizable SPR Microdisplacement Sensor Based on Fiber V-Groove

Abstract

It is difficult to further improve the sensitivity of fiber surface plasmon resonance (SPR) microdisplacement sensor, and it is also unable to identify the direction of microdisplacement. In this article, a high-sensitivity direction recognizable SPR microdisplacement sensor based on fiber V-groove was designed and fabricated. By CO2 laser, the V-groove was fabricated on the graded index multimode fiber, and the SPR effect was produced on the inclined plane of the sensing area by the microdisplacement beam. By controlling the flare angle of the fabricated V-groove, the SPR incident angle was adjusted, so as to effectively increase the microdisplacement sensing sensitivity. The simulation and test results indicate that the sensor with the V-groove flare angle of 88° has the wavelength average sensitivity of 5.26 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and the intensity average sensitivity of 0.032 a.u./ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . In order to solve the problem of microdisplacement direction identification, a dual V-groove structure microdisplacement sensor was designed and fabricated. When the microdisplacement direction is different, the transmission beam contacts different V-grooves, and the microdisplacement direction can be identified by the moving direction of the resonance valley. The proposed sensor greatly improves the sensitivity of optical fiber SPR microdisplacement detection and can identify the direction of microdisplacement, which has the potential application value in the field of precision displacement and positioning.