Position dispersion and optical limiting resulting from thermally induced nonlinearities in Chinese tea liquid

We employ the z-scan method to distinguish thermally induced nonlinearities from others by varying the beam waist radius and to determine the thermo-optic coefficient of materials. One can attribute the origin of optical nonlinearities of Chinese tea liquid to laser-heating-induced nonlinear refraction while one irradiates the media with a cw He-Ne laser. We also analyze the influence of position dispersion on optical limiting.