Nanometer-scale bi-layer metamaterial for near-infrared gas sensing

The advancement of nanofabrication techniques has enabled the precise engineering of subwavelength structures for light localization. Recently, strategies such as bound states in the continuum (BICs), localized surface plasmon resonances (LSPRs), guided mode resonances (GMRs) and microcavities have attracted significant attention. By confining light to a small spatial region, these structures enhance light–matter interactions, which is critical for various applications. One prominent application is gas sensing, where localized optical fields can significantly improve detection sensitivity by amplifying the interaction between light and gas molecules. Here, we present a nanometer-scale bi-layer metamaterial structure designed for gas sensing applications. Subwavelength nanostructures are fabricated on silicon-on-glass (SOG) wafers, which are subsequently bonded using SU-8 adhesive bonding to form a monolithic integrated device. The SU-8 layer serves both as the bonding medium and as a microfluidic channel, which is pre-patterned during fabrication. This bi-layer metamaterial, enabled by SU-8 bonding technology, functions as a compact gas sensor. The proof-of-concept device operates in the near-infrared spectral range with a narrow bandwidth. Nevertheless, the platform can be readily extended to other infrared wavelengths, paving the way for broadband, multi-gas sensing capabilities.