Plasmonic metasurfaces enabling compact long-wave infrared spectrometers

Background. Long-wave infrared spectroscopy is a critical technology for applications such as chemical identification and thermal imaging. However, the widespread adoption of conventional spectrometers is hindered by their large size and complex optics, which are unsuitable for portable or integrated systems. Aim. This study presents a miniaturized alternative: an on-chip spectrometer based on a plasmonic metasurface. Methods. The core component is an array of nine metasurface filters, each engineered to function as a wavelength-selective band-stop filter within the long-wave infrared band. The system processes transmission measurements from these filters with a reconstruction algorithm. Results. The system reconstructs random spectra with fidelities above 94 %, demonstrating robust performance. Furthermore, it effectively distinguished between the characteristic absorption spectra of common solvents, such as methanol and acetic acid, proving its practical sensing utility. Conclusion. These results confirm that the metasurface-based spectrometer is a viable and promising platform for long-wave infrared spectral analysis. Its simple structure, compatible with standard fabrication processes pave the way for highly compact, cost-effective, and portable spectroscopic systems.