Sulfamide: A Promising Deep-Ultraviolet Nonlinear Optical Crystal Assembled from Polar Covalent [SO 2 (NH 2 ) 2 ] Tetrahedra.

For the first time, the polar covalent tetrahedron [SO 2 (NH 2 ) 2 ] is revealed as a new deep-ultraviolet (DUV) nonlinear optical (NLO)-active unit according to theoretical calculations. Furthermore, sulfamide consisting of polar [SO 2 (NH 2 ) 2 ] units was confirmed as an excellent candidate as a DUV NLO crystal. Sulfamide provides the optimal balance between composition, structure, and properties, in addition to a very short absorption of 160 nm. It achieves multiple optical performance records for non-π-conjugated DUV NLO materials, including the strongest second harmonic generation (SHG) efficiency (about 4 times that of KDP), the largest birefringence (obv.: 0.07@589.3 nm) and the shortest SHG wavelength predicted as 188 nm.