Wide band gap selenide infrared nonlinear optical materials AMgGaSe with strong SHG responses and high laser-induced damage thresholds.

Infrared (IR) nonlinear optical (NLO) materials with strong NLO response, wide band gap and high laser-induced damage threshold (LIDT) are highly expected in current laser technologies. Herein, by introducing double alkaline-earth metal (AEM) atoms, three wide band gap selenide IR NLO materials AMgGaSe (A = Ca, Sr, Ba) with excellent linear and NLO optical properties have been rationally designed and fabricated. AMgGaSe (A = Ca, Sr, Ba) are composed of unique [ASe] triangular prisms, [MgSe] octahedra and [GaSe] tetrahedra. The introduction of double AEMs effectively broadens the band gaps of selenide-based IR NLO materials. Among them, CaMgGaSe, achieving the best balance between the second-harmonic generation response (∼1.5 × AgGaS), wide band gap (2.71 eV), high LIDT (∼9 × AgGaS), and moderate birefringence of 0.052 @ 1064 nm, is a promising NLO candidate for high power IR laser. Theoretical calculations indicate that the NLO responses and band gaps among the three compounds are mainly determined by the NLO-active [GaSe] units. The results enrich the chemical diversity of chalcogenides, and give some insight into the design of new functional materials based on the rare [ASe] prismatic units.