Highly Sensitive U-Shaped Micro-channel Photonic Crystal Fiber–Based Plasmonic Biosensor

A simple design of photonic crystal fiber (PCF)–based surface plasmon resonance (SPR) sensor is proposed and investigated numerically for the detection of large analyte refractive index (RI) range. An open U-shaped analyte channel is introduced at the top side and along the length of the fiber to detect unknown analytes. The U-shaped channel helps to generate large amount of surface plasmon resonance on the plasmonic metal layer (gold) by reducing the distance between core and sensing medium. The optical properties and sensitivity of the sensor are analyzed by using the finite element method. The simulation results suggest that the sensor can detect analyte refractive index ranging from 1.33 to 1.44 with maximum wavelength sensitivity of 66,000 nm/RIU and resolution of 1.52 × 10⁻⁰⁶ RIU. It also exhibits the maximum amplitude sensitivity of 2,940 RIU⁻¹ with sensor resolution of 3.40 × 10⁻⁰⁵ RIU. Furthermore, a good figure of merit (FOM) of 1734 RIU⁻¹ and maximum limit of detection (LOD) of 2.29 × 10⁻¹¹ RIU²/nm are achieved by the proposed sensor. Additionally, the fabrication tolerance in terms of pitch, air-hole diameter and channel size is investigated. Finally, we can anticipate that the sensor will be a suitable candidate to detect unknown analytes such as biological or biochemical samples for its high sensitivity with wide sensing range.