Measurement of nonlinear absorption coefficients of organic materials by mode-mismatched Z-scan thermal lensing technique

We evaluate a new pump-probe mode-mismatched thermal lens (TL) scheme for the measurement of nonlinear absorption in nitrobenzene, benzene, and chloroform. In this new scheme the pump beam is focused in the presence of a collimated probe beam. Values of the nonlinear absorption coefficients of the materials studied for the wavelength of 532 nm are reported, and we compare the proposed technique with the well-known open Z-scan method.