INFRARED TO ULTRAVIOLET MEASUREMENTS OF 2-PHOTON ABSORPTION AND N(2) IN WIDE BANDGAP SOLIDS

The bound electronic nonlinear refractive index, n(2), and two-photon absorption (2PA) coefficient, beta, are measured in a variety of inorg anic dielectric solids at the four harmonics of the Nd:YAG laser using Z scan, The specific materials studied are: barium fluoride (BaF2), c alcite (CaCO3), potassium bromide (KBr), lithium fluoride (LiF), magne sium fluoride (MgF2), sapphire (Al2O3), a tellurite glass (75%TeO2 + 2 0%ZnO + 5%Na2O) and fused silica (SiO2). We also report n(2) and beta in three second-order, chi((2)), nonlinear crystals: potassium titanyl phosphate (KTiOPO4 or KTP), lithium niobate (LiNbO3), and beta-barium berate (beta-BaB2O4 or BBO). Nonlinear absorption or refraction can a lter the wavelength conversion efficiency in these materials, The resu lts of this study are compared to a simple two-parabolic band model or iginally developed to describe zincblende semiconductors, This model g ives the bandgap energy (E(g)) scaling and spectrum of the change in a bsorption, The dispersion of n(2) as obtained from a Kramers-Kronig tr ansformation of this absorption change scales as E(g)(4-). The agreeme nt of this theory to data for semiconductors was excellent, However, a s could be expected, the agreement for these wide bandgap materials is not as good, although general trends such as increasing nonlinearity with decreasing bandgap energy can be seen.