Fig. 23: Adaptation performances of metalenses in the extreme environment.

SEM images of the TiO₂ metalens as-fabrication (a), after chemical contaminants (b), and after self-cleaning (c), scale bar: 10 μm, with corresponding focus efficiencies (d) under different incident wavelength. e The focusing efficiencies of the diamond metalens before and after treatment in different chemical, including 2 h immersion in KOH, H₂SO₄, a mixture of HNO₃ and HCl, as well as the grit blasting processing. f SEM images of four representative materials (ZnO, GaN, Si, and diamond) before and after the same grit blasting processing. g Extreme environment testing process (thermal stress cycle) with an all-glass metalens with a diameter of 1 cm. h SEM images of the metalens before and after 15 cycles of the thermal stress cycle. i Microscope images of the metalens before and after 20 min vibrational stress. j The focusing FWHMs of the metalens at different frequencies under different hydrostatic pressure. k Photograph of the contact angle of a water droplet on the surface of the metalens (with nanostructures). Inset: photograph of the contact angle of a water droplet on the surface of the substrate (without nanostructures). l Schematic of thermal drift effect of 4H-SiC metalens (left) and conventional objective lens (right). Cross-sectional images (bottom) show the cutting performance on a 4H-SiC substrate before and after 60 min operation. a–d Reprinted with permission from ref. ³¹¹. Copyright 2020 John Wiley and Sons. e, f Reprinted with permission from ref. ²⁴⁶. Copyright 2024 John Wiley and Sons. g–i Reprinted with permission from ref. ⁹⁷. Copyright 2024 American Chemical Society. j Reprinted with permission from ref. ³¹⁵. Copyright 2022 Elsevier. k Reprinted with permission from ref. ³¹². Copyright 2023 American Chemical Society. l Reprinted with permission from ref. ³¹⁷. Copyright 2024 John Wiley and Sons