Infrared to Ultraviolet Measurements of Two-Photon Absorption and n2 in Wide Bandgap Solids
UNIVERSITY OF CENTRAL FLORIDA ORLANDO CENTER FOR RESEARCH AND EDUCATION IN OPTICS AND LASERS
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The bound electronic nonlinear refractive index, nsub 2, and two-photon absorption 2PA coefficient, beta, are measured in a variety of inorganic dielectric solids at the four harmonics of the NdYAG laser using Zeta scan. The specific materials studied are barium fluoride BaF2, calcite CaCO3, potassium bromide KBr, lithium fluoride LiF, magnesium fluoride MgF2, sapphire AbO3, a tellurite glass 75Te0z20ZnO 5Na2O and fused silica SiO2. We also report n2 and beta in three second-order, chiexpn 2, nonlinear crystals potassium titanyl phosphate KTiOPO4 or KTP, lithium niobate LiNbO3, and beta-barium borate beta-BaB2O4 or BBO. Nonlinear absorption or refraction can alter the wavelength conversion efficiency in these materials. The results of this study are compared to a simple two-parabolic band model originally developed to describe zincblende semiconductors. This model gives the bandgap energy Esub 9 scaling and spectrum of the change in absorption. The dispersion of nsub 2 as obtained from a Kramers-Kronig transformation of this absorption change scales as Esub g expn-4. The agreement of this theory to data for semiconductors was excellent. However, as 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.
- Electricity and Magnetism
- Atomic and Molecular Physics and Spectroscopy
- Solid State Physics