Synthesis of new thioborate crystals for non-linear optical application

Abstract

<p>New thioborate crystals have been synthesized to search for novel infrared non-linear optical (NLO) materials having large optical non-linear properties combined with favorable laser damage thresholds and wide transmission ranges from the visible to mid-infrared. In this work, new thioborate crystals are being investigated that have the potential to overcome the low laser damage thresholds of the NLO chalcopyrite sulfide materials without losing their large non-linear properties and wide transmission ranges. New thioborates, Ba7(BS3)4S, Ag3(BS3)2, and Zn[subscript x]Ba2B2S5+[subscript x] (x ~ 0.2) phases were prepared and the structures have been studied by single crystal and powder x-ray diffraction analysis and Infrared and Raman spectroscopy. While the Ba7(BS3)4S and Ag3(BS3)2 phases crystallize in the cetrosyrnmetric monoclinic space group C2/c and P2(l)/c, respectively, the Zn[subscript x]Ba2B2S5+[subscript x] (x ~ 0.2) phase crystallizes in the non-centrosymmetric tetragonal space group I4̄ 2m with unit cell parameters of a = 4.771 Å and c = 24.038 Å, and is based on isolated (BS3)3− structural units. The second harmonic generation (SHG) efficiency determined on powders of Zn[subscript x]Ba2B2S5+[subscript x] (x ~ 0.2) is ~ 50 times larger than that of c-SiO2. The infrared spectra show transparency from 2.5 [Mu]m to 10 [Mu]m with absorption bands around 12 [Mu]m related to the vibration modes of (BS3)3− units. UV-visible-near-infrared spectra show that it is transparent in the visible region down to ~350 nm, which is a large improvement over the absorption edge of AgGaS2 at 490 nm and also suggest that it can have a large laser damage threshold.</p>