Design and analysis of a tunable refractive index sensor by using a Ta2O5-coated photonic crystal fiber

A plasmonic refractive index (RI) sensor based on photonic crystal fiber is proposed. A chemically stable thin film of gold (Au) is used as an active plasmonic layer and high RI material Ta2O5 is used as an overlayer over the gold thin film. The effect of Ta2O5 thin film on the sensor performance is analyzed in detail and a novel, as per the authors' best knowledge, operating analyte RI range tunable property is reported. It is observed that the operating range is tuned toward the lower RI region with increasing Ta2O5 layer thickness. Furthermore, the sensor is optimized and its sensitivity is realized using both wavelength and amplitude interrogation techniques. A maximum wavelength sensitivity and amplitude sensitivity of 16,354 nm/RIU (refractive index unit) and 1574 RIU-1, respectively, are obtained corresponding to the operating RI range of 1.39 to 1.41 for the optimized structure. Moreover, the detection accuracy of the sensor is found of the order of 10(-6) with a high figure of merit up to 282 representing an overall good sensing performance. The sensor performance is realized using surface plasmon resonance phenomenon and numerically analyzed using finite element method. Our study, no doubt, provides a new direction of designing RI sensor that could tune the RI range to the desired operating range. In addition, the simple design feasibility, low fabrication cost, and portable nature of the proposed sensor make it suitable for industrial and chemical sensing applications. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)

Automated summary

A plasmonic refractive index sensor based on photonic crystal fiber with a chemically stable gold thin film and Ta2O5 overlayer is proposed. The sensor shows tunable analyte RI range, high sensitivity, and detection accuracy. Its design feasibility, low fabrication cost, and portability make it suitable for industrial and chemical sensing applications.