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Proceedings Paper

Femtosecond Dynamics Of Fluoro-Aluminum Phthalocyanine And Linear Alkane Molecules
Author(s): Z. Z. Ho; V. Williams; N. Peyghambarian; W. M. Hetherington
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Paper Abstract

The dynamics of fluoro-aluminum phthalocyanine polycrystalline thin films is studied using differential transmission spectroscopy with femtosecond laser pulses. Following excitation by 620 nm pulses into the first electronic transition a very rapid energy redistribution of the excitons is directly observed within the 55 fs duration of the pump pulse. Following this process two extremely fast decay routes lead to the recovery of the ground state : exciton-exciton annihilation with an intensity dependent decay of 550 fs at power density of 1.2 GW/cm2 and exciton-phonon coupling with a 4 ps decay time. A complete interpretation of the decay mechanisms based on the Frenkel exciton terminology successfully accounts for the observed results. We have analyzed the nonlinear dynamics of a series of linear alkane molecules in pure liquid state using the time-resolved optical Kerr effect. The results show that the Kerr nonlinearity increases linearly with the number of atoms. However, for those molecules with more than eight carbons, a surprisingly large deviation from the bond additivity approximation was observed. The molecular orientational contribution to the nonlinear response is negligible for these types of molecules. A small component, with less than 8% of the total nonlinear Kerr response, is attributed to translational anisotropy and has a 450 fs lifetime. The nonlinear dynamics and the length dependence of optical Kerr nonlinearities will be discussed.

Paper Details

Date Published: 21 December 1988
PDF: 8 pages
Proc. SPIE 0971, Nonlinear Optical Properties of Organic Materials, (21 December 1988); doi: 10.1117/12.948265
Show Author Affiliations
Z. Z. Ho, University of Arizona (United States)
V. Williams, University of Arizona (United States)
N. Peyghambarian, University of Arizona (United States)
W. M. Hetherington, Oregon State University (United States)

Published in SPIE Proceedings Vol. 0971:
Nonlinear Optical Properties of Organic Materials
Garo Khanarian, Editor(s)

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