Achieving broadband ultraviolet to mid-infrared transparency in germanate-based nonlinear optical crystals Cs3REGe3O9 (RE = Y, Gd)

Two novel Cs 3 REGe 3 O 9 (RE = Y, Gd) crystals were extracted and exhibit a breakthrough of UV cutoff edge at 210 and 215 nm, respectively, the shortest value among boron-free germanate-based NLO materials.