Highly Sensitive Surface Plasmon Resonance Sensor Based on Graphene-Coated U-shaped Fiber
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Highly Sensitive Surface Plasmon Resonance Sensor Based on Graphene-Coated U-shaped Fiber Tianqi Xie1 · Ying He1
· Yanfang Yang1 · Huifang Zhang1 · Yi Xu2
Received: 30 June 2020 / Accepted: 18 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract A graphene-coated U-shaped fiber surface plasmon resonance sensor with high refractive index sensitivity is proposed. With the combination of graphene coating and U-shape design, the proposed sensor exhibits a significantly enhanced sensitivity as compared with the conventional Au-based straight fiber surface plasmon resonance sensor. The refractive index sensitivity of 15.52 μm/RIU (refractive index unit) is achieved by coating monolayer graphene on U-shaped fiber with a bent radius of 1.1 cm. A sensitivity enhancement factor of about 5-fold is obtained when compared with the conventional straight fiber surface plasmon resonance sensor with and without monolayer graphene coating. The effect of Au thickness, number of graphene layers, and the bent radius on the sensor performance was investigated. The high sensitivity of the proposed graphene-coated U-shaped fiber surface plasmon resonance sensor makes it a promising candidate for biosensing and chemical sensing. Keywords Surface plasmon resonance sensor · Graphene · U-shaped fiber · High sensitivity
Introduction Surface plasmon resonance (SPR) sensors, a type of optical sensors, have been widely employed for sensing applications in chemistry, biology, environmental monitoring, food industry, and clinical diagnostics due to their high sensitivity, stability, and reliability [1–4]. Various SPR sensor structures have been proposed and demonstrated in recent years [3], in which the prism-coupled Kretschmann configuration [5] is the most widely used SPR structure. However, the SPR sensors based on Kretschmann configuration are usually bulky due to the employment of bulky prism. In contrast, fiber SPR sensor has small footprint, low cost, and remote sensing capability [6]. A variety of fiber structures have been proposed to improve the sensitivity of fiber SPR Ying He
[email protected] Yi Xu
yi [email protected] 1
Department of Physics, College of Science, Shanghai University, Shangda Road 99, Shanghai, 200444, China
2
Engineering Product Development, Singapore University of Technology and Design, Singapore, 487372, Singapore
sensor, including side-polished fiber [7], tapered fiber [8, 9], hetero-core structured fiber [10, 11], and U-shaped fiber [12, 13]. For example, R. K. Verma et al. proposed a SPR sensor based on uniform semi-metal-coated U-shaped fiber [12]. It is found that 25 times sensitivity can be achieved with the U-shaped fiber SPR sensor as compared with the conventional straight fiber SPR sensor. In recent years, two-dimensional (2D) materials (e.g., graphene and transition metal dichalcogenides) have been extensively exploited in sensing due to their high surfaceto-volume ratio and biocompatibility [3, 14–24]. The integration of 2D materials makes SPR s
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