Optical nonlinearities of tea studied by Z-scan and four-wave mixing techniques

Optical nonlinearities of black-tea extract dissolved in water are studied using the Z-scan and the four-wave mixing techniques with 7-ns, 532-nm pulses from a Q-switched Nd:YAG laser. The magnitude of the third-order nonlinear optical susceptibility of tea in water is comparable with that of carbon disulfide. The nonlinearity is identified to be of thermal origin.