Multidimensional Cation Modulation toward Phase-Matchable Nonlinear Optical Fluorides with Short UV Cutoff Edges

Deep-ultraviolet (DUV) transparent nonlinear optical (NLO) materials with phase-matchable second-harmonic generation (SHG) are essential for laser frequency conversion, yet their rational design remains challenging. Herein, three fluoride compounds, K3Ba2Hf6F31 and KRbBaM2F12 (M = Zr, Hf), were synthesized via a multidimensional cation modulation strategy consisting of two independent routes: central metal substitution and partial alkali cation substitution. Optical measurements reveal that three compounds show short ultraviolet cutoff edges below 200 nm and phase-matchable SHG responses, with SHG intensities ranging from 0.4 to 0.6 times that of KH2PO4. This work demonstrates that multidimensional cation modulation provides an effective strategy for obtaining fluorides toward DUV transparent NLO materials.