Enhanced third-order nonlinear optical responses from optically pumped electronic excited states

Abstract

In this paper, we review the microscopic description for nonlinear optical processes originating from populated electronic excited states and examine an enhancement mechanism for third order optical processes. For a general case, we consider the third order (formula available in paper) excited state susceptibilities for linear chains that have been previously well-studied for their ground state nonlinear optical properties. We see that for a given frequency, enhancement can occur in the excited state (formula available in paper) and the origin and mechanism of the enhancement can be directly understood in terms of new virtual excitation processes. In section III, we summarize a recently completed experimental study of enhanced excited state third harmonic generation in conjugated structures.