LAUSR

Extreme ultraviolet (EUV) radiation is a key technology for material science, attosecond metrology, and lithography. Here, we experimentally demonstrate metasurfaces as a superior way to focus EUV light. These devices exploit the fact that holes in a silicon membrane have a considerably larger refractive index than the surrounding material and efficiently vacuum-guide light with a wavelength of ~50 nanometers. This allows the transmission phase at the nanoscale to be controlled by the hole diameter. We fabricated an EUV metalens with a 10-millimeter focal length that supports numerical apertures of up to 0.05 and used it to focus ultrashort EUV light bursts generated by high-harmonic generation down to a 0.7-micrometer waist. Our approach introduces the vast light-shaping possibilities provided by dielectric metasurfaces to a spectral regime that lacks materials for transmissive optics. Description Pushing metalenses to extremes The fields of ultrafast spectroscopy and semiconductor photolithography rely on very short wavelengths, typically in the extreme ultraviolet (EUV) realm. However, most optical materials strongly absorb light in this wavelength regime, resulting in a lack of generally available transmissive components. Ossiander et al. designed and fabricated a metalens in which a carefully engineered array of holes in a thin silicon membrane focuses ultrafast EUV pulses close to the diffraction limit by “vacuum guiding.” The results open up transmissive optics to the EUV regime. —ISO Metalens technology can be pushed into the extreme ultraviolet wavelength regime.