Optical properties of a quinoid molecule

Abstract

We report on linear and third order nonlinear optical properties of the quinoid molecule 5,5 ′-bis(3,5-di- tert-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)-5,5 ′-dihydro-2, 2 ′-bithiophene.Variable angle spectroscopic ellipsometry has been used to determine the dispersion of the dielectric in a spectral range from the near infrared to the near ultraviolet. We have measured a high value of the index of refraction in the transparency region (i.e., n=1.886 at λ=1.5 μ m), indicating the high polarisability of the molecule under study. The nonlinear optical properties have been measured by third harmonic generation in the near infrared spectral range. At λ=1.5 μ m the nonlinear coefficient of the molecule has been estimated to be 4.2 × 10 −19 m 2/V 2 (3.0 × 10 −11 esu).