Spatial Frequency Manipulation of a Quartz Crystal for Phase‐Matched Second‐Harmonic Vacuum Ultraviolet Generation

Abstract Second harmonic generation (SHG) is the nonlinear response of electrons to high‐intensity light and has been successfully applied in basic scientific research and modern optoelectronics. However, constrained by stringent but essential phase‐matching conditions, efficient vacuum ultraviolet (VUV) SHG is still a challenge in solid‐state lasers. Here, this work employs a spatial frequency manipulation strategy to realize artificially structured phase‐matching conditions in ordinary quartz crystals for efficient frequency doubling in the VUV range. Phase‐matched VUV SHG at wavelengths of 177.3 and 167.8 nm is realized with unprecedented output power and conversion efficiency. The design strategy releases the phase‐matching condition for nonlinear optics and provides a way to study light–matter nonlinear interactions, and the present sources should be helpful for the development of VUV photonics, including high‐resolution angle‐resolved photoemission spectroscopy and Al+ optical clocks.