Femtosecond laser irradiation of molecular excitonic films for nanophotonic response control and large-area patterning

Abstract

Molecular excitonic films such as J-aggregate thin films can show an optically metallic response in the visible region and can be considered as alternative materials for plasmonics. However, there was no direct, top-down method to modify the optical response over a large area. Here, we demonstrate the femtosecond (fs) laser processing of J-aggregate films on the centimeter scale. With proper laser conditions, optically metallic films (Re[epsilon] < 0) were modified to dielectric ones (Re[epsilon] > 0) with large changes in optical responses. We performed various optical spectrum measurements to investigate the effect of fs-laser irradiation. Our results demonstrate that the strong modification of the optical response can be induced over a large area by fs-laser processing and this can be useful for novel nanophotonic studies. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement