BaGa2SnSe6: a new phase-matchable IR nonlinear optical material with strong second harmonic generation response

Abstract

By introducing heavy Sn ions to a Ba–Ga–Q system, a new IR nonlinear optical material, BaGa₂SnSe₆, has been obtained. It crystallizes in space group R3 of the trigonal system with a = 10.1449(14) Å, c = 9.2490(18) Å and Z = 3. In the structure, three (Ga/Sn)Se₄ tetrahedra are connected via corner-sharing to generate (Ga/Sn)₃Se₉ building groups, which are further joined to produce a three-dimensional network with Ba²⁺ lying in the cavities. Due to the contribution of the large and easily-polarizable Sn atom and the polar arrangements of the (Ga/Sn)Se₄ tetrahedra, the compound exhibits a very strong NLO response, i.e., ∼5.2 times that of the benchmark AgGaS₂ at a fundamental laser wavelength of 2.09 μm and shows type-I phase-matchable behavior. Furthermore, the calculated birefringence index is Δn = 0.1649 at 1.064 μm and the major SHG tensors are d₁₁ = 62.91 pm V⁻¹ and d₃₃ = 50.26 pm V⁻¹.