Continuous-wave laser-based polarization-modulated maskless lithography with parallel meta-atom exposure for millimeter-scale LWIR metalenses.

Abstract

Long-wave infrared (LWIR) metalenses are important for compact thermal imaging and remote sensing applications, and a rapid, cost-effective, and high-precision fabrication method is highly desirable. Here, we propose polarization-modulated maskless digital lithography based on a continuous-wave (CW) laser and a spatial light modulator (SLM). One SLM mask encodes N×N independently defined meta-atom patterns, transferred simultaneously to photoresist in one exposure through polarization-based phase-to-intensity conversion and demagnified 4f projection. Compared with sequential single-meta-atom exposure, the number of exposure steps is reduced to approximately 1/N2. Using this approach, we fabricated a 3 mm × 3 mm LWIR metalens with a numerical aperture of 0.25 at 10.6 µm. The device exhibits a measured focal-length error of 1% and a focusing efficiency of 54.7%. The CW laser significantly simplifies the system architecture, reducing capital equipment requirements and enabling a cost-effective and accessible platform for scalable fabrication of LWIR metasurfaces.