Electric field induced second harmonic generation (EFISH) experiments in the swivel cell: New aspects of an established method

The EFISH technique is well known and widely used to determine the efficiency of the second harmonic generation (SHG) of liquid samples. In the first part of this paper, a simple and convenient experimental setup for EFISH measurements is presented. A standard photometric cell was used and the cell was swiveled during the experiments. The mathematical treatment of the data included corrections for the SHG of the optical cells and the solvent. The second part of the paper deals with the measurements of compounds which showed notable absorption at the SHG wavelength. In addition to the contributions of the solvent and the cell to the SHG signal the molar absorption coefficient of the compound and the refractive indices for the ground and the second harmonic wave of the solution were included in the processing of the EFISH data. Results of these measurements were in good agreement with those which others have obtained by independent methods. Thus the swivel method allowed estimation of the SHG (in terms of μβ where μ is the dipole moment of the molecule and β is the second-order polarizability) of non-absorbing, weakly absorbing and notably strongly absorbing compounds by easy-to-perform EFISH measurements.