Near‐Zero Reflection via Mie‐Resonant Metasurfaces for Boosted LWIR Response in InAs/GaSb Superlattice Detector

All‐dielectric metasurfaces supporting both electric and magnetic Mie resonances exhibit exceptional capabilities for optical field manipulation, thereby opening new avenues for the development of optoelectronics. However, their electromagnetic response characteristics and applications in the long‐wave infrared (LWIR) spectrum remain relatively unexplored. In this study, a Mie‐resonant amorphous silicon metasurface to enhance LWIR response of the InAs/GaSb superlattice detector is designed. The scattering characteristics of a single amorphous silicon microdisk are investigated as functions of disk radii and heights by the finite‐difference time‐domain simulation. When assembled into a periodic square array, these amorphous silicon microdisks exhibit strong directional radiation arising from electric and magnetic multipole resonances, leading to the appearance of distinct reflection valleys at resonant wavelengths. Furthermore, benefiting from the leaky modes induced by the substrate, these reflection valleys broaden into a near‐zero reflection region spanning 8–13 µm upon integration with the GaSb substrate. Experimental results confirm that InAs/GaSb LWIR detectors integrated with the amorphous silicon metasurface yield a broadband photoresponse enhancement, with the responsivity at 8–13 µm increasing by 0.28–0.77 A W −1 . This work sheds light on the performance enhancement of long‐wave infrared detectors via all‐dielectric metasurfaces engineering.