Deep (DUV, 200 – 280 nm) and vacuum ultraviolet (VUV, 100 – 200 nm) light has many important applications ranging from photodissociation to lithography. However, the generation and manipulation of electromagnetic radiation in this wavelength regime remains challenging. Popular sources like excimer lasers are bulky and many traditional optical materials suffer from strong absorption in this short wavelength regime. In this thesis, I experimentally demonstrate how nonlinear metasurfaces provide an alternative approach to simultaneously generate and control such radiation. Metasurfaces are composed of highly engineered subwavelength nanostructures, called meta-atoms, that give them the exceptional ability to manipulate the amplitude, phase, and polarization of the light they are interacting with. The ability of meta-atoms to strongly confine the local electric field, enables enhancement of nonlinear processes like second (SHG) and third harmonic generation (THG). This allows the conversion of longer wavelength radiation to the DUV and VUV regime via a compact device. In addition, unlike nonlinear crystals, nonlinear metasurfaces do not require phase matching due to their subwavelength interaction length. Local phase control via meta-atoms makes it possible to manipulate the output wavefront of a metasurface. In this way, nonlinear metasurfaces can be used not just for the generation but also the manipulation of DUV and VUV light.

This thesis consists of three main parts. The first part presents a plasmonic metasurface consisting of gold nanostructures on top of an indium tin oxide (ITO) thin film that were designed to exhibit a toroidal resonance at the pump wavelength of 785 nm. The nanostructures can generate an electric field enhancement pattern that reaches into the underlying ITO layer, where it enhances THG to generate DUV light at 262 nm. The nonlinear signal from the toroidal metasurface is about five times larger than that of a dimer metasurface fabricated for comparison with the same amount of gold per unit area and underlying ITO layer.

The second part presents an all-dielectric metasurface consisting of titanium dioxide (TiO2) nanostructures designed to facilitate an anapole resonance around the pump wavelength of 555 nm. An anapole resonance is caused by an interference between an electric and a toroidal dipole mode giving rise to exceptional electric field enhancement. Here, this is utilized to enhance THG and produce VUV light at 185 nm. Notably, the observed nonlinear signal from the nonlinear metasurface is around 180 times stronger compared to an unpatterned TiO2 substrate of the same thickness.

In the third part, multifunctional nonlinear metasurfaces for VUV generation and manipulation are demonstrated. They consist of zinc oxide (ZnO) nanotriangles that show a magnetic dipole resonance around the pump wavelength of 394 nm that was designed to boost SHG. Geometric rotation of individual nanotriangles allows for local phase manipulation via the geometric phase, when excited with circularly polarized light. In this way, nonlinear metasurfaces for both focusing and beam steering of VUV light are demonstrated.