Z-SCAN MEASUREMENTS OF THE NONLINEAR REFRACTION IN RETINAL DERIVATIVES

The nonlinear refractive index, n(2), of 13-cis retinal aldehyde, 13-c is retinoic acid and all-trans retinoic acid were determined. For 13-c is retinal aldehyde solutions which were left to age for a few days, a n increase of over one order of magnitude for n(2) was observed. With basis on the comparison of infrared spectra of freshly prepared and ag ed solutions, we suggest that the enhancement of the nonlinear respons e is associated to a spontaneous cis to trans isomerization of the ret inal molecule. The second order hyperpolarizabities of all the retinal derivatives were also inferred from the measurements. (C) 1997 Elsevi er Science B.V.