Two-photon absorption measurements in organic liquids via nonlinear light mixing spectroscopy

Abstract

Using the three‐wave mixing (3WM or CARS) experiment, the absorptive and dispersive parts of the two‐photon absorption (TPA) process in liquid CS₂, CHCl₃, C₆H₁₂ and their mixtures with naphthalene were accurately measured relative to known Raman cross sections of the solvents in the range 35 0001−1. The measurement is based on the interference effects between different processes which coherently contribute to the third‐order nonlinear susceptibility χ⁽³⁾ measured in the mixing experiment. It is shown that the parametric mixing measurement is superior to the classical TPA measurements. The TPA cross sections obtained here will be useful for the calibration of classical TPA measurements.