Design, modeling and experimental characterization of a patch antenna for SWIR/MWIR detection

Abstract This paper presents the design, simulation, and performance characterization of a metamaterial patch antenna array specifically engineered for infrared (IR) radiation detection in the 2–5 μ m wavelength range, covering the Short-Wave Infrared (SWIR) and Mid-Wave Infrared (MWIR) spectral regions. Mid-IR detection is gaining increasing interest owing to its broad applications in environmental monitoring, chemical and gas sensing, thermal imaging, and free-space optical communications. The proposed structure consists of a periodic array of AlSi metallic resonant patches with a 1 μ m pitch and 200 nm gap between adjacent patches. These patches are deposited on a dielectric stack backed by an AlCu metallic reflector, forming an optical resonant cavity. Two different dielectric configurations were investigated. The first consists of a single dielectric layer: Tetra-Ethyl-Ortho-Silicate (TEOS) approximately 1 μ m thick, deposited on an AlCu reflector. The second comprises a double-layer stack: a 1.3 μ m TEOS layer over a 0.7 μ m amorphous silicon (a-Si) layer, also deposited on an AlCu reflector. Total reflectance measurements were performed using Fourier Transform Infrared Spectroscopy (FTIR). The experimental results were compared with an analytical model and full-wave electromagnetic simulations using the Finite Element Method (FEM) in ANSYS HFSS software. The fabricated device exhibits strong absorption peaks at wavelengths of 2.6 μ m , 3.0 μ m, and 4.0 μ m, effectively covering the SWIR and MWIR bands. The absorption spectrum can be tuned over a wide range from SWIR to MWIR and potentially extendable to Long-Wave infrared (LWIR) by adjusting the antenna geometry and dielectric stack composition. The proposed structures show strong potential for applications requiring IR spectral selectivity such as gas sensing and other optoelectronic devices operating in the SWIR and MWIR regions.