Distinction of two-photon absorption from other nonlinear loss mechanisms by phase-conjugate interferometry

Abstract

We show that phase-conjugate interferometry is a measuring technique for third-order optical nonlinearities that can distinguish two-photon absorption from other nonlinear loss mechanisms. For the case of 3,3′-diethyloxadicarbocyanine iodide at 1064 nm, the nonlinear loss is dominated by linear absorption from the two-photon excited state. We observe a highly nonlinear absorption process in solutions of 4-methoxy-4′-nitrostilbene at 532 nm and show that it is due to a more complicated loss mechanism. This mechanism could have applications in optical limiting.