Cascaded Second Harmonic Generation for Deep‐UV Radiations with a 2D Nonlinear Photonic Quartz Crystal.

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]