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.

Metasurfaces get ultrafast pulses into shape: Nanostructured metasurfaces have been designed to function as many passive optical elements. Now, Divitt et al. demonstrate that metasurfaces can also be operated as time-dependent active optical elements. They used an array of dielectric metasurfaces to demonstrate pulse shaping of ultrashort (femtosecond) pulses in the near-infrared by manipulating the phase and amplitude of the frequency components. The results present a path for the development of dynamic metasurfaces as a platform for miniaturized optical technology with advanced time-dependent functionality. Science , this issue p. 890

Augmented reality (AR) display superimposes virtual texts or images on top of what a person can already see, enabling connection between the physical world and the digital world.^{1 – 7} AR display creates an interwoven experience where digital information alters the user’s perception of the real world and brings new opportunities for highly immersive human–machine interaction. The technology draws huge attention from both academia and industry and has a variety of applications ranging from facilitating decision-making to education and daily entertainment.^{8 – 10} During the ongoing global pandemic, the demand for AR display and related technologies has soared as these technologies avoid the need for travel and social contact, and at the same time, provide immersive virtual presence for remote communications.¹¹

Recent years have witnessed a rapid development in the field of structural coloration, colors generated from the interaction of nanostructures with light. Compared to conventional color generation based on pigments and dyes, structural color generation exhibits unique advantages in terms of spatial resolution, operational stability, environmental friendliness, and multiple functionality. Here, we discuss recent development in structural coloration based on layered thin films and optical metasurfaces. This review first presents fundamentals of color science and introduces a few popular color spaces used for color evaluation. Then, it elaborates on representative physical mechanisms for structural color generation, including Fabry–Pérot resonance, photonic crystal resonance, guided mode resonance, plasmon resonance, and Mie resonance. Optimization methods for efficient structure parameter searching, fabrication techniques for large‐scale and low‐cost manufacturing, as well as device designs for dynamic displaying are discussed subsequently. In the end, the review surveys diverse applications of structural colors in various areas such as printing, sensing, and advanced photovoltaics.