SrZnGeS4: A Dual‐Waveband Nonlinear Optical Material with a Transparency Spanning UV/Vis and Far‐IR Spectral Regions

Non-linear optical chalcogenides with a wide band gap (Eg ) and excellent NLO properties are key materials for highly desirable multiwaveband tunable optical parametric oscillators (OPOs). We exploit the "electronic structure engineer bucket effect" to develop a novel dual-waveband SrZnGeS4 with an ultrawide transparency window. It exhibits an asymmetric Fdd2 structure that consists of layers formed by corner-sharing [ZnGeS6 ] dimers. SrZnGeS4 is transparent from 0.30 to 23.6 μm, spanning the UV-, vis-, mid- and far-IR spectral regions and has the widest Eg (3.63 eV) in the AeMII MIV Q4 family to date. It exhibits phase matching, high SHG intensities (e.g., 11.0×KDP and 17.5×AGS under λinc =1450 and 950 nm, respectively), and a very high laser-induced damage threshold (35×AGS). These results not only suggest bright prospects for high-power laser applications but may also enable applications of the multiwaveband OPO system from the UV-visible to far-IR regions.