Design and numerical analysis of a gold-coated photonic crystal fiber based refractive index sensor

Abstract

In the course of past decade, surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensors have shown phenomenal advancement. Many researchers have proposed a wider range of SPR-based sensors by this time. But many of these proposed sensors either show low sensitivity or it is very difficult to fabricate the sensors for real time applications. We present a simple circular shaped PCF SPR sensor which is easy to fabricate as well as shows high sensitivity in the visible and near-infrared spectroscopy. A chemically stable and inactive plasmonic material, gold is applied to the outer layer of the PCF structure to generate surface plasmon excitation. A perfectly matched layer is used to minimize radiation absorption towards the surface. The guiding properties and analytical evaluation are carried out using commercially available COMSOL Multiphysics version 5.4 on the basis of finite element method. In x-polarization mode, the maximal value of amplitude sensitivity and wavelength sensitivity (WS) of the proposed sensor is 1757.3RIU−1 (Refractive Index Unit) and 32,000 nm/RIU respectively. In addition to that, the proposed design exhibits high sensor resolution of 1.428 × 10–6 and figure of merit of 587.2 indicating a high-performance sensor and demonstrates birefringence of 0.004 RIU. Moreover, the proposed PCF-SPR sensor is composed of only six symmetrical circular air holes, which makes it fabrication friendly. Owing to the high performance of the proposed sensor and high fabrication probability makes the sensor a strong contender to be used in biomedical and biochemical applications.