A new class of molecules with large, switchable vibrational non-linear optical responses: Photochromic diarylethene systems

Photochromic diarylethene molecules are characterized by electronic properties significantly different in the two isomers. In this work, we are particularly concerned with the vibrational contribution to second order hyperpolarizabilities. We show that a systematic increase of the non-linear optical properties is observed every time the closure reaction is induced by a suitable irradiation. The large change of molecular non-linear optical coefficients can be exploited e.g., for the realization of an optical switch. Moreover, we show that also the intrinsic response of the “closed” (i.e., more conjugated) form is, in some case, quite large. The structural reasons of this phenomenon are discussed.