Wide band gap selenide infrared nonlinear optical materials AIIMg6Ga6Se16 with strong SHG responses and high laser-induced damage thresholds

Abstract

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 A^IIMg₆Ga₆Se₁₆ (A^II = Ca, Sr, Ba) with excellent linear and NLO optical properties have been rationally designed and fabricated. A^IIMg₆Ga₆Se₁₆ (A^II = Ca, Sr, Ba) are composed of unique [A^IISe₆] triangular prisms, [MgSe₆] octahedra and [GaSe₄] tetrahedra. The introduction of double AEMs effectively broadens the band gaps of selenide-based IR NLO materials. Among them, CaMg₆Ga₆Se₁₆, achieving the best balance between the second-harmonic generation response (∼1.5 × AgGaS₂), wide band gap (2.71 eV), high LIDT (∼9 × AgGaS₂), 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 [GaSe₄] units. The results enrich the chemical diversity of chalcogenides, and give some insight into the design of new functional materials based on the rare [A^IISe₆] prismatic units.