Monochromatic UV metalens with continuous zoom capability via metasurface rotation

The dynamic focal length modulation in the ultraviolet band is essential for applications such as biological imaging and lithography. Conventional approaches, however, often depend on intricate mechanical systems, limiting their efficiency and precision. Here, we propose a double-layer metasurface architecture that enables continuous and wide-range focal length tuning by the relative rotation between the upper and lower metasurfaces, without axial displacement. Our simulations demonstrate that under 380 nm illumination, the proposed structure maintains an average transmittance exceeding 0.8, with performance approaching the diffraction limit. Furthermore, by incorporating circular polarization selectivity, the lens enables rapid focal length polarity inversion simply by switching the handedness of the incident light, the theoretical adjustment range can reach from -∞ to +∞. This work provides a compact solution for high-performance ultraviolet focusing systems.