title: Unusual and tunable one-photon nonlinearity in gold-dye plexcitonic Fano systems.
abstract: Recent studies of the coupling between the plasmonic excitations of metallic nanostructures with the excitonic excitations of molecular species have revealed a rich variety of emergent phenomena known as plexcitonics. Here, we use a combined experimental and theoretical approach to demonstrate new and intriguing aspects in the ultrafast nonlinear responses of strongly coupled hybrid Fano systems consisting of gold nanorods decorated with near-infrared dye molecules. We show that the severely suppressed linear absorption around the Fano dip significantly enhances the unidirectional energy transfer from the plasmons to the excitons and further allows one-photon nonlinearity to be drastically and reversibly tuned. These striking observations are interpreted within a microscopic model stressing on two competing processes: saturated plasmonic absorption and weakened destructive Fano interference from the bleached excitonic absorption. The unusually strong one-photon nonlinearity revealed here provides a promising strategy in fabricating nanoplasmonic devices with both pronounced nonlinearities and good figures of merit.
authors.affiliation: †Department of Physics, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Fan
authors.initials: F
authors.lastname: Nan
authors.affiliation: †Department of Physics, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Ya-Fang
authors.initials: YF
authors.lastname: Zhang
authors.affiliation: ‡Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong 518055, People's Republic of China.|§International Center for Quantum Design of Functional Materials (ICQD), University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Li
authors.affiliation: §International Center for Quantum Design of Functional Materials (ICQD), University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Xiao-Tian
authors.initials: XT
authors.lastname: Zhang
authors.affiliation: ∥State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, People's Republic of China.
authors.forename: Hang
authors.initials: H
authors.lastname: Li
authors.affiliation: ∥State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, People's Republic of China.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Zhang
authors.affiliation: ⊥Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR People's Republic of China.
authors.forename: Ruibin
authors.initials: R
authors.lastname: Jiang
authors.affiliation: ⊥Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong SAR People's Republic of China.
authors.forename: Jianfang
authors.initials: J
authors.lastname: Wang
authors.affiliation: #Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: †Department of Physics, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
authors.affiliation: †Department of Physics, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Jia-Hong
authors.initials: JH
authors.lastname: Wang
authors.affiliation: †Department of Physics, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.|∇Institute for Advanced Study, Wuhan University, Wuhan, Hubei 430072, People's Republic of China.
authors.forename: Qu-Quan
authors.initials: QQ
authors.lastname: Wang
authors.affiliation: §International Center for Quantum Design of Functional Materials (ICQD), University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Zhang
keywords: Fano interference; Gold nanorod; one-photon nonlinearity; plexciton resonance; ultrafast energy transfer