Saturation of Depth and Polarization of Resonant and Satellite Spectral Holes Generated with Pulsed Laser Excitation

Abstract

We consider photochemical hole burning of an inhomogeneous and isotropic ensemble of chromophores through excitation with a narrow-bandwidth source of polarized light. We derive expressions for the depth and anisotropy of resonant and vibronic satellite spectral holes with increasing fluence. A fit of these saturation curves to experimental data yields the Debye-Waller factor of the system. A simple rate equation model predicts that the anisotropy of a spectral hole depends only on the angle between the transition dipoles of the burnt and the probed transitions. In experiments with pulsed lasers strong deviations from this ideal behavior are observed. An extended theory including saturation gives a satisfactory description of this phenomenon and provides a new method for the determination of photochemical quantum yields.