An Enhanced Plastic Optical Fiber-Based Surface Plasmon Resonance Sensor with a Double-Sided Polished Structure.

Lian Liu,Chuanxin Teng,Hongchang Deng,Shijie Deng,Libo Yuan,Jie Zheng

doi:10.3390/s21041516

Abstract

An enhanced plastic optical fiber (POF)-based surface plasmon resonance (SPR) sensor is proposed by employing a double-sided polished structure. The sensor is fabricated by polishing two sides of the POF symmetrically along with the fiber axis, and a layer of Au film is deposited on each side of the polished region. The SPR can be excited on both polished surfaces with Au film coating, and the number of light reflections will be increased by using this structure. The simulation and experimental results show that the proposed sensor has an enhanced SPR effect. The visibility and full width at half maximum (FWHM) of spectrum can be improved for the high measured refractive index (RI). A sensitivity of 4284.8 nm/RIU is obtained for the double-sided POF-based SPR sensor when the measured liquid RI is 1.42. The proposed SPR sensor is easy fabrication and low cost, which can provide a larger measurement range and action area to the measured samples, and it has potential application prospects in the oil industry and biochemical sensing fields.

Highlights

Surface plasmon resonance (SPR) sensors are very sensitive to the small changes of refractive index (RI); after decades of development, they have been widely investigated in biochemical sensing fields, such as environmental monitoring, food safety, and disease diagnosis [1,2]
We proposed an enhanced plastic optical fiber (POF)-based SPR sensor by employing a double-sided polished structure
This structure can excite the SPR effect on both sides of the fiber–Au film interfaces, which can increase the number of light reflections and bring an enhanced effect

Summary

Introduction

Surface plasmon resonance (SPR) sensors are very sensitive to the small changes of refractive index (RI); after decades of development, they have been widely investigated in biochemical sensing fields, such as environmental monitoring, food safety, and disease diagnosis [1,2]. Compared with the single-mode fiber, the multimode fiber has a large core diameter, which could maintain a good mechanical strength even after the side-polishing or tapering process; in addition, the coupling efficiency between the multimode fiber and the broadband light sources is higher. N. Cennamo et al investigated the effects of different photoresist buffer layers on the POF-based SPR sensor performance [25], and a POF-SPR-based magnetic field sensor [26]. Introduced a tapered structure to the side polished POF-based SPR sensor as the modal filter to optimize the SPR spectrum [29], and they compared the sensing performances for the D-shaped tapered POFs-based SPR sensors with different taper ratios [30]. Teng et al [31] optimized the sensing performance of the side-polished U-shape POF-based SPR sensor. The proposed sensor probe is easy fabrication, low cost, and possesses a good mechanical strength, which can provide a larger measurement range and action area to the measured samples without increasing the sensor length

Sensor Structure and Operation Principle

Experimental Results and Discussions

Conclusions