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Proceedings Paper

Experimental study of the second-order nonlinear scattering properties of a helicene molecule
Author(s): Koen J. Clays; Kurt Wostyn; Andre P. Persoons; Stefano Maiorana; Claude A. Daul
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Paper Abstract

We evaluate the theoretical potential of a series of donor-acceptor-substituted helicenes. Different synthetic approaches towards the parent tetrathia-(7)-helicene TH(7) and the formyl derivative are described. Femtosecond hyper-Rayleigh scattering (HRS) experiments as a function of amplitude modulation (AM) frequency on the parent helicene molecule have been performed. The apparent first hyperpolarizability βapp(ω) is a decreasing function of increasing AM frequency ω, due to the two-photon fluorescence (2PF) contribution. We observe, however, for the first time, also an AM frequency-dependent HRS depolarization ratio ρ(ω). For dipolar respectively octopolar chromophores, ρ for HRS and 2PF is identical (5 respectively 1.5) and, therefore, constant as the fluorescence contribution decreases. For this helicene molecule here, we now see an increase in depolarization ratio for increasing AM frequency. An accurate value for ρ is important, since it offers an indication for the symmetry of the chromophore. The limiting value for ρ(ω) at high frequencies, i.e. ρ∞ without 2PF contribution, is in agreement with the theoretical value obtained from a purely helicoidal symmetry, i.e. a helicene without electron donor or acceptor groups.

Paper Details

Date Published: 10 November 2003
PDF: 12 pages
Proc. SPIE 5212, Linear and Nonlinear Optics of Organic Materials III, (10 November 2003); doi: 10.1117/12.503813
Show Author Affiliations
Koen J. Clays, Katholieke Univ. Leuven (Belgium)
Kurt Wostyn, Katholieke Univ. Leuven (Belgium)
Andre P. Persoons, Katholieke Univ. Leuven (Belgium)
Stefano Maiorana, Univ. degli Studi di Milano (Italy)
Claude A. Daul, Univ. of Fribourg (Switzerland)

Published in SPIE Proceedings Vol. 5212:
Linear and Nonlinear Optics of Organic Materials III
Mark G. Kuzyk; Manfred Eich; Robert A. Norwood, Editor(s)

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