Adduct-Type IR Nonlinear-Optical Crystal SbI₃·(S₈)₃ with a Large Second-Harmonic Generation and a High Laser-Induced Damage Threshold

A noncentrosymmetric adduct, SbI₃·(S₈)₃, is obtained by a facile solution method. It crystallizes in the trigonal space group R3m, and its structure features van der Waals force connected, isolated trigonal-pyramidal SbI₃ and chairlike S₈ units. SbI₃·(S₈)₃ exhibits strong second-harmonic-generation responses around 4 times that of KH₂PO₄ (1.064 μm) and 1 times that of AgGaS₂ (AGS; 2.1 μm) at 210–250 μm, respectively. Under both laser-radiation wavelengths, it exhibits type I phase-matching behavior. Its laser-induced damage threshold is measured to be around 26 times that of AGS under 1.064 μm. To better understand these optical data, theoretical calculations are performed to address its electronic structure and optical properties.