Stabilization of the Polar Structure and Giant Second‐Order Nonlinear Response of Single Crystal γ‐NaAs<sub>0.95</sub>Sb<sub>0.05</sub>Se<sub>2</sub>
Abishek K. Iyer, Jingyang He, Hongyao Xie, Devin Goodling, Duck Young Chung, Venkatraman Gopalan, Mercouri G. Kanatzidis
Abstract
Abstract The dearth of suitable materials significantly restricts the practical development of infrared (IR) laser systems with highly efficient and broadband tuning. Recently, γ‐NaAsSe 2 is reported, and it exhibits a large nonlinear second‐harmonic generation (SHG) coefficient of 590 pm V −1 at 2 µm. However, the crystal growth of γ‐NaAsSe 2 is challenging because it undergoes a phase transition to centrosymmetric δ‐NaAsSe 2 . Herein, the stabilization of non‐centrosymmetric γ‐NaAsSe 2 by doping the As site with Sb, which results in γ‐NaAs 0.95 Sb 0.05 Se 2 is reported. The congruent melting behavior is confirmed by differential thermal analysis with a melting temperature of 450 °C and crystallization temperature of 415 °C. Single crystals with dimensions of 3 mm × 2 mm are successfully obtained via zone refining and the Bridgman method. The purification of the material plays a significant role in crystal growth and results in a bandgap of 1.78 eV and thermal conductivity of 0.79 Wm −1 K −1 . The single‐crystal SHG coefficient of γ‐NaAs 0.95 Sb 0.05 Se 2 exhibits an enormous value of | d 11 | = 648 ± 74 pm V −1 , which is comparable to that of γ‐NaAsSe 2 and ≈20× larger than that of AgGaSe 2 . The bandgap of γ‐NaAs 0.95 Sb 0.05 Se 2 (1.78 eV) is similar to that of AgGaSe 2 , thus rendering it highly attractive as a high‐performing nonlinear optical material.