Experimental study of the second-order nonlinear scattering properties of a helicene molecule

Koen J. Clays; Kurt Wostyn; Andre P. Persoons; Stefano Maiorana; Claude A. Daul

doi:10.1117/12.503813

10 November 2003 Experimental study of the second-order nonlinear scattering properties of a helicene molecule

Koen J. Clays, Kurt Wostyn, Andre P. Persoons, Stefano Maiorana, Claude A. Daul

Proceedings Volume 5212, Linear and Nonlinear Optics of Organic Materials III; (2003) https://doi.org/10.1117/12.503813
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

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.

Citation Download Citation

Koen J. Clays, Kurt Wostyn, Andre P. Persoons, Stefano Maiorana, and Claude A. Daul "Experimental study of the second-order nonlinear scattering properties of a helicene molecule", Proc. SPIE 5212, Linear and Nonlinear Optics of Organic Materials III, (10 November 2003); https://doi.org/10.1117/12.503813

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