Efficiency of two-photon absorption in single-frequency and multifrequency laser radiation fields

An experimental study was made of the dependence of the two-photon absorption of neodymium laser radiation in an alcohol solution of rhodamine 6G on the intensity of the excitation field under the following conditions: single-frequency emission, emission of 3–5 axial modes, and emission of a large number of longitudinal modes (≈300). It was found that the efficiency of the two-photon absorption in the field of 3–5 modes was 1.5 times higher and the corresponding absorption in the multifrequency field and 2.1 times higher than the efficiency of absorption in the single-frequency field.