CHIRALITY IN NONLINEAR OPTICS AND OPTICAL SWITCHING

Chirality in molecular opto-electronics is limited sofar to the use of optically active liquid crystals and a number of optical phenomena ar e related to the helical macroscopic structure obtained by using one e nantiomer, only. In this paper, the use of chirality in nonlinear opti cs and optical switching is demonstrated. The additional options offer ed by the combination of circularly polarized light and chiral molecul es gives rise to the observation of Second Harmonic Generation from ce ntrosymmetric crystals of a racemic mixture. This phenomenon is due to the existence of optical activity in the hyperpolarizability. Chiropt ical switching is observed in inherently dissymmetric molecules, that can undergo a photochemical isomerization of a strongly dextrorotatory isomer into a strongly laevorotatory isomer. Using circular dichroism the switching between these two pseudo-enantiomers can be monitored a ccurately.