Measurement of the Two-photon Absorption Coefficient of Gallium Phosphide (GaP) Using a Dispersion-minimized Sub-10 Femtosecond Z-scan Measurement System

Report No. ARL-TR-6157
Authors: Robert C. Hoffman and Andrew G. Mott
Date/Pages: September 2012; 24 pages
Abstract: This report describes the measurement of the two-photon absorption coefficient of gallium phosphide (GaP) at 9.4 fsec as measured with a unique Z-scan measurement system designed to support the shortest possible laser pulses. The Z-scan system is designed to minimize dispersion of the ultrashort laser pulse as it propagates so that the shortest possible pulse reaches the sample, as well support the entire 220-nm bandwidth of the pulse. Using the standard laboratory and analysis methods of Sheik-Bahae et al., we obtain a two-photon absorption coefficient, β, of GaP of 1.02 cm/GW at 800 nm, a value commensurate with measurements at performed at longer pulse widths. To the best of our knowledge, this is the first determination of the two-photon absorption coefficient of GaP below 10 fsec.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2012