Color pixels composed of plasmonic nanostructures provide a highly promising approach for new display technologies, capable of vivid, robust coloration and incorporating the use of low-cost plasmonic materials, such as aluminum. Here we report a plasmonic device that can be tuned continuously across the entire visible spectrum, based on integrating a square array of aluminum nanostructures into an elastomeric substrate. By stretching the substrate in either of its two dimensions, the period and therefore the scattering color can be modified to the blue or the red of the at-rest structure, spanning the entire visible spectrum. The unique two-dimensional design of this structure enables active mechanical color tuning, under gentle elastic modulation with no more than 35% strain. We also demonstrate active image switching with this structure. This design strategy has the potential to open the door for next-generation flexible photonic devices for a wide variety of visible-light applications.

Vacuum ultraviolet (VUV) light has important applications in many fields, ranging from device fabrication to photochemistry, from environmental remediation to microscopy and spectroscopy. Methods to produce coherent VUV light frequently utilize high harmonic generation in media such as rare gases or atomic vapors; nonlinear optical crystals that support second harmonic generation into the VUV are quite rare. Here, we demonstrate an all-dielectric metasurface designed for the nonlinear optical generation of VUV light. Consisting of an array of zinc oxide nanoresonators, the device exhibits a magnetic dipole resonance at a wavelength of 394 nm. When excited with ultrafast laser pulses at this wavelength, the second harmonic at 197 nm is readily generated. Manipulation of the metasurface design enables control over the radiation pattern. This work has the potential to open the door toward simple and compact VUV sources for new applications.

The harmonic generation of light with plasmonic and all-dielectric nanostructures has gained much recent interest. This approach is especially promising for short wavelength (i.e., ultraviolet (UV)) generation, where conventional nonlinear crystals reach their limits both in transparency and in their ability to achieve phase-matching between the input and output fields. Here, we demonstrate that the third harmonic generation of deep UV light in an indium tin oxide (ITO) film can be substantially enhanced by a metasurface consisting of metallic toroidal meta-atoms covered with an alumina layer for protection against laser-induced damage. This approach combines the benefits of the large nonlinear susceptibility of ITO with the unique field enhancement properties of a toroidal metasurface. This ITO–meta-atom combination produces a third harmonic signal at a wavelength of 262 nm that is nominally five times larger than that of an ITO film patterned with a conventional hotspot-enhanced plasmonic dimer array. This result demonstrates the potential for toroidal meta-atoms as the active engineered element in a new generation of enhanced nonlinear optical materials and devices.

Dielectric metasurfaces have recently been shown to provide an excellent platform for the harmonic generation of light due to their low optical absorption and to the strong electromagnetic field enhancement that can be designed into their constituent meta-atoms. Here, we demonstrate vacuum ultraviolet (VUV) third harmonic generation from a specially designed dielectric metasurface consisting of a titanium dioxide (TiO 2 ) nanostructure array. The metasurface was designed to enhance the generation of VUV light at a wavelength of 185 nm by tailoring its geometric design parameters to achieve an optical resonance at the fundamental laser wavelength of 555 nm. The metasurface exhibits an enhancement factor of nominally 180 compared to an unpatterned TiO 2 thin film of the same thickness, evidence of strong field enhancement at the fundamental wavelength. Mode analysis reveals that the origin of the enhancement is an anapole resonance near the pump wavelength. This work demonstrates an effective strategy for the compact generation of VUV light that could enable expanded access to this useful region of the electromagnetic spectrum.

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.