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Harmonic generation can broaden the laser wavelength in a great scope and is rich in physics, but the efficient cascaded second harmonic generation especially those directly deep into deep‐ultraviolet (DUV) with one single crystal seems to be impossible, due to the extremely strict phase‐matching conditions and relative narrow bandgap of present nonlinear optical crystals. Here, this work designs a nonlinear photonic quartz crystal where the phase difference of interacted light waves is manipulated in two dimensions and realizes an unprecedented cascaded phase‐matched 2nd–5th harmonic generation simultaneously with the photon energy up to 6 eV, representing the shortest wavelength by cascaded second harmonic generation in the solid‐state nonlinear medium. The generated light is located in the visible‐DUV region with a total conversion efficiency of 2.7%. The present nonlinear photonic quartz scheme not only provides a multi‐wavelength solid‐state laser source applied in modern devices but also develops a new route for studying the light‐matter nonlinear interaction in the DUV region. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]