Precise alignment of a longitudinal Pockels cell for time-resolved circular dichroism experiments

Artifacts in time-resolved circular dichroism experiments are carefully analyzed. We show that alignment of the longitudinal Pockels cell that modulates the laser polarization in such experiments is crucial. By developing a calculation of the behavior of a slightly misaligned Pockels cell, we are able to propose a simple alignment procedure. This procedure is based on the use of an analyzer at 0° or 45° of the Pockels cell axes, and it allows us to improve the alignment by 3 orders of magnitude and to reduce the artifact below the noise level in our experimental setup.