Vacuum ultraviolet nonlinear metalens

Abstract

Vacuum ultraviolet (VUV) light plays an essential role across science and technology, from molecular spectroscopy to nanolithography and biomedical procedures. Realizing nanoscale devices for VUV light generation and control is critical for next-generation VUV sources and systems, but the scarcity of low-loss VUV materials creates a substantial challenge. We demonstrate a metalens that both generates—by second-harmonic generation—and simultaneously focuses the generated VUV light. The metalens consists of 150-nm-thick zinc oxide (ZnO) nanoresonators that convert 394 nm (~3.15 eV) light into focused 197-nm (~6.29 eV) radiation, producing a spot 1.7 μm in diameter with a 21-fold power density enhancement as compared to the wavefront at the metalens surface. The reported metalens is ultracompact and phase-matching free, allowing substantial streamlining of VUV system design and facilitating more advanced applications. This work provides a useful platform for developing low-loss VUV components and increasing the accessibility of the VUV regime.

Revisiting Optical Material Platforms for Efficient Linear and Nonlinear Dielectric Metasurfaces in the Ultraviolet, Visible, and Infrared

“…Recently, higher efficiencies have been recorded for ZnO metalenses, whose spatial phase profiles are engineered with geometric phases. The ZnO metalenses have focused vacuum UV (λ = 197 nm) under a fundamental λ of 394 nm and achieved conversion and focusing efficiencies of 6 × 10 –9 and 0.39%, respectively …”

“…The ZnO metalenses have focused vacuum UV (λ = 197 nm) under a fundamental λ of 394 nm and achieved conversion and focusing efficiencies of 6 × 10 −9 and 0.39%, respectively. 95 Additionally, LiNbO 3 nanocubes have been used to enhance conversion efficiencies with SHG. LiNbO 3 has hexagonal noncentrosymmetric crystals with low optical losses in the near-UV region, which provide efficient nonlinear SHG conversion.…”

Deep-ultraviolet nonlinear optical crystals: concept development and materials discovery

“…In addition, advances in quasi-phase matching or new phase matching continues 91 , 92 . The development of photonic crystals and metamaterials may bring new opportunities for the design of NLO crystals 93 , 94 . All in all, after more than ten years of development, although possible structures with DUV NLO properties or even exceeding KBBF have been discovered from time to time, there are basically no practical crystals and no effective DUV harmonic output being reported.…”

Large-scale achromatic flat lens by light frequency-domain coherence optimization

“…Conventional refractive lens has achieved great success in the area of imaging, metrology, detection, etc 1,2 , but its bulky and heavy characteristics prevent the systems from being compact, lightweight, and miniaturized, which is in high demand for portable and convenient applications 3 . Metalenses, made of subwavelength nano-unit cells with ultrathin, lightweight, and flat architecture, do provide possible solutions that to some extent overcome the shortcomings of conventional diffractive lens with higher focusing efficiency and weak shadow-effect [4][5][6][7][8][9] . However, metalenses still severely suffer from poor imaging quality under broadband illumination due to serious chromatic aberration [10][11][12][13] .…”