Metasurface-Enhanced Tellurium Thin-Film Mid-Infrared Photodetector

The design of photodetectors tailored to specific wavelengths in the mid-infrared (MIR) band serves as a foundational enabler for advancements in scientific research, industrial inspection, and environmental monitoring. Metasurfaces, composed of artificially engineered subwavelength unit cells, enable precise tailoring of light–matter interactions, achieving near-unity absorption at target wavelengths and thereby significantly boosting the sensitivity and spectral selectivity of MIR photodetectors. In this study, we developed a double-C open-loop metasurface and optimized its geometric parameters to realize high-efficiency absorption at 4 μm and 6 μm. Utilizing Te thin films fabricated via magnetron sputtering, we constructed a metasurface-enhanced mid-infrared photodetector based on Te thin films. The optimized metasurface structure enhances the light absorption of the Te thin film by a factor of eight within the target wavelength band. Ultimately, the metasurface-enhanced Te-based device achieved responsivities of 10.5 A/W and 13.7 A/W at 4 μm and 6 μm, respectively, representing enhancements of 3.6-fold and 3-fold compared to the initial Te thin-film device. This work provides a critical reference for enhancing the detection performance of infrared photodetectors at specific wavelengths through precise nanophotonic design.