Abstract
Shrinking conventional optical systems to chip-scale dimensions will benefit custom applications in imaging, displaying, sensing, spectroscopy, and metrology. Towards this goal, metasurfaces—planar arrays of subwavelength electromagnetic structures that collectively mimic the functionality of thicker conventional optical elements—have been exploited at frequencies ranging from the microwave range up to the visible range. Here, we demonstrate high-performance metasurface optical components that operate at ultraviolet wavelengths, including wavelengths down to the record-short deep ultraviolet range, and perform representative wavefront shaping functions, namely, high-numerical-aperture lensing, accelerating beam generation, and hologram projection. The constituent nanostructured elements of the metasurfaces are formed of hafnium oxide—a loss-less, high-refractive-index dielectric material deposited using low-temperature atomic layer deposition and patterned using high-aspect-ratio Damascene lithography. This study opens the way towards low-form factor, multifunctional ultraviolet nanophotonic platforms based on flat optical components, enabling diverse applications including lithography, imaging, spectroscopy, and quantum information processing.
Highlights
An optical metasurface is a planar array of subwavelength electromagnetic structures that emulate the operation of a conventional refractive, birefringent, or diffractive optical component, such as a lens, waveplate, or hologram, through individually tailored amplitude, phase, or polarization transformations of the incident light[1,2,3,4,5,6,7,8,9]
This achievement opens the way for low-form-factor and multifunctional photonic systems based on UV flat optics, and suggests promising applications in photolithography, highresolution imaging, UV spectroscopy and quantum information processing
The choice of HfO2—a material most commonly exploited for its high static dielectric constant as a transistor gate insulator in complementary metal oxide semiconductor (CMOS) integrated circuits—is guided by the promise of both a large refractive index (n > 2.1 for λ0 < 400 nm) and a wide bandgap Eg = 5.7 eV located well within the deep-UV range, leading to a negligible extinction coefficient (k ≈ 0) for λ0 ≥ λg
Summary
An optical metasurface is a planar array of subwavelength electromagnetic structures that emulate the operation of a conventional refractive, birefringent, or diffractive optical component, such as a lens, waveplate, or hologram, through individually tailored amplitude, phase, or polarization transformations of the incident light[1,2,3,4,5,6,7,8,9]. We implement metasurfaces designed for operation at three representative UV wavelengths of 364, 325, and 266 nm, which perform a variety of optical functions, namely, high-numerical-aperture lensing, accelerating beam generation, and hologram projection, including under spin control for the last two applications. This achievement opens the way for low-form-factor and multifunctional photonic systems based on UV flat optics, and suggests promising applications in photolithography, highresolution imaging, UV spectroscopy and quantum information processing
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