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

Abstract Non‐linear optical chalcogenides with a wide band gap ( E g ) 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 SrZnGeS 4 with an ultrawide transparency window. It exhibits an asymmetric Fdd2 structure that consists of layers formed by corner‐sharing ZnGeS 6 dimers. SrZnGeS 4 is transparent from 0.30 to 23.6 μm, spanning the UV‐, vis‐, mid‐ and far‐IR spectral regions and has the widest E g (3.63 eV) in the AeM II M IV Q 4 family to date. It exhibits phase matching, high SHG intensities (e.g., 11.0×KDP and 17.5×AGS under λ inc =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.