Electrically Reconfigurable Phase Change Material-Based Metamaterial Absorber for Broadband Molecular Fingerprint Retrieval

Abstract

Chalcogenide phase-change materials (PCMs) exhibit low absorption losses in the mid-infrared (MIR) region, which can be exploited for MIR photonic applications. Furthermore, they show a significant change in the optical properties with phase transformation. Surface-enhanced infrared absorption spectroscopy using metamaterials has shown great potential for detecting molecular fingerprint vibrations in the MIR region. However, these metamaterials have a very narrow bandwidth, limiting the range of molecular fingerprint detection. In this work, we numerically demonstrate a PCM-based metamaterial absorber for molecular fingerprint retrieval in the MIR region. By modulating the phase of the PCM, i.e., Ge2Sb2Te5, the resonant absorption of the metamaterial can be tuned to a broad range. Temporal coupled-mode theory is employed to determine the optimal design of the tunable metamaterial for enhanced sensitivity. By manipulating the phase of the PCM and employing two metapixels, we demonstrate a wide detection range spanning from 940 to 1860 cm–1. We use this technique to detect distinct vibrational fingerprints of different analytes, such as poly(methyl methacrylate) and protein. Furthermore, we show that by integrating the sensing platform with a microheater, the resonant absorption can be dynamically reconfigured by applying voltage pulses. Our results indicate that the proposed tunable sensor holds promise for detecting multiple molecular signatures and chemical identification. We believe that this work paves the way toward an effective and miniaturized design of optical sensors in the MIR region.