Drastic effects of damping mechanisms on the third-order optical nonlinearity

Abstract

We have investigated the optical response of superradiant atoms, which undergoes three different damping mechanisms: radiative dissipation (${\gamma }_r$), dephasing (${\gamma }_d$), and nonradiative dissipation (${\gamma }_n$). Whereas the roles of ${\gamma }_d$ and ${\gamma }_n$ are equivalent in the linear susceptibility, the third-order nonlinear susceptibility drastically depends on the ratio of ${\gamma }_d$ and ${\gamma }_n$: When ${\gamma }_d\ll {\gamma }_n$, the third-order susceptibility is essentially that of a single atom. Contrarily, in the opposite case of ${\gamma }_d\gg {\gamma }_n$, the third-order susceptibility suffers the size-enhancement effect and becomes proportional to the system size.

5pages, 2figures