Measuring the dynamics of circular dichroism in a pump-probe experiment with a Babinet-Soleil compensator

Circular dichroism contains rich information on the conformation of molecules and, in particular, of biomolecules, and measuring its variation in a pump-probe experiment is very promising but also very challenging. We propose a new technique to measure pump-induced variation of the circular dichroism, which is based on the measurement of the probe ellipticity and its variation with the pump. This technique has the advantage that it does not require modulation of the probe polarization, which allows modulation of the pump intensity. We show theoretically and demonstrate experimentally that this technique is very sensitive and user friendly. We also show that it can be used to measure pump-induced change in the optical rotation, allowing for a complete characterization of pump-induced optical activity.