Measurement of nonlinear refraction by using double T-PO technique

A transmittance technique with a phase object (T-PO) is a new method to investigate the optical nonlinearity of the materials. However, in this technique, the optical nonlinear coefficient is obtained by using the complicated numerical simulation. Based on the T-PO technique, a double T-PO technique was presented. In double T-PO technique, a reference light path of T-PO was added into the original T-PO setup, a sample under test and a standard sample were placed in the focal plane of measurement and reference T-PO setup, respectively. The intensities in the focal plane of these two T-PO were adjusted to be equal. The nonlinear refraction index can be obtained conveniently by comparing the normalized nonlinear transmittance of the sample under test and the standard sample. Double T-PO technique has several advantages, such as no displacement of the nonlinear medium, single pulse measurement. Furthermore, the technique avoids the complicated numerical simulation.