Ultra-broadband mid-infrared plasmonic sensor based on soft-glass photonic crystal fiber for refractive index and temperature detection

Abstract

We introduce a new plasmonic sensor employing a soft-glass photonic crystal fiber configuration for ultra-broadband high-sensitivity refractive index and temperature detection. The analyte channel contains one gold nanowire for plasmonic excitation. A thorough analysis of the sensing characteristics is numerically studied, and the simulation findings indicate that a squeezing lattice structure with one gold nanowire can significantly strengthen the interaction between the y-polarized core mode and surface plasmon polaritons mode across the mid-infrared (MIR) wavelength, leading to complete mode coupling and better detection performance. Through structural optimization, the sensor can achieve single-resonance sensing over the MIR wavelength range of 3.3–5.3 μm for the analyte RI varying in an ultra-broad range of 1.26–1.50. A peak sensitivity of −18 400 nm RIU−1 coupled with a high RI resolution of −5.43 × 10−6 RIU is obtained, alongside an average sensitivity of −6766.2 nm RIU−1 demonstrating high linearity (0.9968). Additionally, temperature detection from −60 to 40 °C is realized within 3.0–3.7 μm wavelengths, achieving a maximum temperature sensitivity of 7.4 nm °C−1, average sensitivity of 6.7878 nm °C−1, and linearity coefficient of 0.9989. Owing to its exceptional performance, this sensor offers broad application potential in environmental monitoring, medical diagnostics, chemical analysis, and industrial safety.