Third-order optical nonlinearities in retinal derivatives and mesoionic compounds

We describe the application of the z-scan technique to determine the nonlinear refractive index of 13-cis retinal aldehyde (13CRA), 13-cis retinoic acid (13CAR), all-trans retinal aldehyde (ATRA) and all-trans retinoic acid (ATAR), whose molecular structures are given.