Experimental study of the third-order optical nonlinearities in Zn1-xAgxSe crystals

The two-photon absorption (TPA) coefficient (beta) and third-order nonlinear optical susceptibility (chi ((3))) of Zn1-xAgxSe (x = 0.08, 0.10, 0.20) crystals were investigated using the transmission and degenerate four-wave mixing methods. The experimental results show that the real and imaginary Darts of the third-order nonlinear optical susceptibility ( chi ((3))) decrease with an increase of Ag content. Theoretical simulations of the TPA coefficient (beta) were performed using pseudopotential band energy structure calculations. We have evaluated that for an Ag content of about 4.5% beta achieves its maximum. A good agreement between theoretically calculated and experimentally measured susceptibilities is achieved.