Wafer‐Scale Functional Metasurfaces for Mid‐Infrared Photonics and Biosensing

Abstract Metasurfaces have emerged as a breakthrough platform for manipulating light at the nanoscale and enabling on‐demand optical functionalities for next‐generation biosensing, imaging, and light‐generating photonic devices. However, translating this technology to practical applications requires low‐cost and high‐throughput fabrication methods. Due to the limited choice of materials with suitable optical properties, it is particularly challenging to produce metasurfaces for the technologically relevant mid‐infrared spectral range. These constraints are overcome by realizing functional metasurfaces on almost completely transparent free‐standing metal‐oxide membranes. A versatile nanofabrication process is developed and implemented for highly efficient dielectric and plasmonic mid‐infrared metasurfaces with wafer‐scale and complementary metal–oxide–semiconductor (CMOS)‐compatible manufacturing techniques. The advantages of this method are revealed by demonstrating highly uniform and functional metasurfaces, including high‐Q structures enabling fine spectral selectivity, large‐area metalenses with diffraction‐limited focusing capabilities, and birefringent metasurfaces providing polarization control at record‐high conversion efficiencies. Aluminum plasmonic devices and their integration into microfluidics for real‐time and label‐free mid‐infrared biosensing of proteins and lipid vesicles are further demonstrated. The versatility of this approach and its compatibility with mass‐production processes bring infrared metasurfaces markedly closer to commercial applications, such as thermal imaging, spectroscopy, and biosensing.