Plasmon augmented two photon absorption in a strongly coupled nano-molecular hybrid

Abstract

A long-standing goal in optical sciences has been to strengthen nonlinear optical effects at lower light powers or pulse energies. In this perspective, strongly-coupled hybrids which offer significant third order optical nonlinearities at low powers are currently a topic of global research. Herein, we report a detailed analysis of third order nonlinear photonic characteristics of the fabricated nanohybrid system. The far field and near field optical coupling between the constituents of the hybrid were investigated using Near field scanning optical microscopy and Raman spectroscopy respectively. While the optical nonlinearity (i.e. two photon absorption in this case) has been elucidated using Z-scan spectroscopy. The experimental outcomes reveal in the linear as well as the nonlinear regime the dye and the Au nanoislands represent a strongly interacting system. A 400% enhancement in the two photon absorption coefficients of an organic dye Eosin Yellow is observed when hybridized with Au nanoislands. The results are explained in terms of the energy transfer from the dye to the hybridized Au nanoislands film. The investigations of such mechanisms, may bring forth exciting advances, not only in terms of strongly interacting photons, but also shed light on the impact of energy transfer mechanisms on third order nonlinearity of nano-molecular hybrids.