Non-Degenerate Two-Photon Absorption in ZnSe: Experiment and Theory

Abstract

We experimentally and theoretically investigate the non-degenerate two-photon absorption coefficient ${\hat{I}}^2(\ddot{I}{‰}_1,\ddot{I}{‰}_2)$ in the prototypical semiconductor ZnSe. In particular, we provide a comprehensive data set on the dependence of ${\hat{I}}^2(\ddot{I}{‰}_1,\ddot{I}{‰}_2)$ on the non-degeneracy parameter $\ddot{I}{‰}_1/\ddot{I}{‰}_2$ with the total frequency sum $\ddot{I}{‰}_1+\ddot{I}{‰}_2$ kept constant. We find a substantial increase of the two-photon absorption strength with increasing $\ddot{I}{‰}_1/\ddot{I}{‰}_2$. In addition, different crystallographic orientations and polarization configurations are investigated. The nonlinear optical response is analyzed theoretically by evaluating the multiband semiconductor Bloch equations including inter- and intraband excitations in the length gauge. The band structure and the matrix elements are taken an eight-band k.p model. The simulation results are in very good agreement with the experiment.

6 pages, 5 figures