Determination of nonlinear absorption (β) and refraction (n2)by the Z-scan method: third-order nonlinear optical properties of π- conjugated Potassium Pentaborate crystal

Potassium Pentaborate nonlinear optical (NLO) material was synthesized by the solution growth method. The grown crystals were subjected to structural, optical and mechanical property studies. Crystal with excellent transparency were grown with maximum size of 9mm×8mm×5mm and the grown crystals were characterized by single crystal Single crystal XRD, FT-IR, TGA-DTA&DSC, and UV–vis-NIR studies. The crystal belongs to orthorhombic with a space group of mm2 having unit-cell dimensions a = 11.068Åb= 11.175Å c = 9.058Åand α = 90°; β = 90°; and γ =90°; Z=4, at 298(2) K. The second-order nonlinear optical property of the polycrystalline sample has been confirmed by Kurtz-Perry powder SHG analysis. Third order nonlinear optical properties were also studied by Z-scan techniques. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also calculated.