Third harmonic generation in perylene derivatives

Abstract

The nonlinear optical properties of a series of tetratert.-butyl-perylene derivatives of different molecular sizes were investigated by means of third harmonic generation. — The nonlinear susceptibilities χ ⁽³⁾(−3ω,ω,ω,ω) of the smaller molecules (biperylenyle, terrylene, quaterrylene) as measured by excitation with a Nd;YaG-laser (wavelength=1064 nm) are in the range of 10⁻¹² esu and are one order of magnitude lower than that of the pentarylene. Its χ ⁽³⁾-value reaches a magnitude greater than 5×10⁻¹¹ esu which is comparable to the χ ⁽³⁾ of linear conjugated polymers. The nonlinear susceptibility of the investigated perylene derivatives increases with the interrelated quantities of the reciprocal of the S ₀ → S ₁-excitation energy, the wavelength of the absorption maximum, and the length of the molecule. Resonance enhancement of the nonlinear susceptibility is observed for the biperylenyle due to a mutual two-photon resonance and for the pentarylene due to both one-photon and three-photon resonance.