High performance extra-ordinary optical transmission based self-referenced plasmonic metagrating sensor in the NIR communication band

Abstract

Simulation of an extra-ordinary optical transmission based self-referenced, flexible plasmonic metagrating has been reported. The metagrating was optimized to work as a refractive index (RI) sensor with high figure of merit (FOM) for near infra-red (NIR) communication band. The metagrating consists of two metal nanoslit arrays (MNSAs) in a manner that the open portion (groove) of the upper MNSA overlaps with the closed portion (pit) of the lower MNSA and vice versa. The metagrating structure was optimized to support dual plasmonic modes; one of them being sensing mode and the other, self-referenced. Transmission efficiency of 57%, the sensitivity of 1147 nm RIU−1, and FOM of 271/RIU were achieved for the analyte RI range 1.30–1.38. This design of metagrating possesses a stronger coupling of electromagnetic (EM) fields between the constituent MNSAs, which results in higher (almost double) transmission efficiency and FOM as compared to trivial MNSAs. Control simulations were performed to understand the role of various parameters on self-referencing operation, to evaluate the fabrication tolerances, and to estimate the performance at various ambient temperatures. The present study will be useful in development of flexible, low-cost, yet performance-enhanced metagrating sensors, which could easily be integrated on the tip of optical fibers working in the NIR communication window.