Discrimination of thermal, molecular orientation, and pure electronic refractive nonlinearities using the polarization-resolved Z-scan technique

Abstract

We have investigated how the polarization-resolved Z-scan technique is able to distinguish and discriminate three types of nonlinear effects—thermal, orientational, and ultrafast electronic nonlinearities—when acting simultaneously. Here employing a high-repetition-rate ultrafast laser, we excite these three nonlinearities in pure and contaminated CS2 solvent. Using 200 fs laser pulses, we could detect and measure the contribution of pure electronic, orientational, and, more importantly, identify the growth of cumulative thermal effect as the laser repetition rate increases. Also, we have verified that the source of the thermal effect is mainly due to two-photon (one-photon) absorption for pure (contaminated) CS2.