New simple method for measuring nonlinear polarization ellipse rotation with high precision using a dual-phase lock-in

Abstract

The measurements of nonlinear ellipse rotation (NER) can be very helpful to determine the magnitude, as well, the origin of the nonlinearity. As it is known, NER is related to particular component of the third-order nonlinear susceptibility which can be different from other nonlinear effects. In this way, here we propose a new method to improve the measuring precision of the NER angle using a dual phase lock-in. We also did a well known Z-scan measurement which provides the nonlinear refractive index to give support to our results. Using these two measurements, we could study several materials nonlinearity with different origin and we could reveal the tensor nature of the refractive nonlinearities. Material with thermal, molecular orientation and nonresonant electronic origins could be easily distinguished by those techniques.