Balci, S.Kocabas, C.Küçüköz, B.Karatay, A.Akhüseyin, E.Yaglioglu, H. G.Elmali, A.2016-02-082016-02-0820140003-6951http://hdl.handle.net/11693/25547We investigate ultrafast energy transfer between excitons and plasmons in ensembles of core-shell type nanoparticles consisting of metal core covered with a concentric thin J-aggregate (JA) shell. The high electric field localization by the Ag nanoprisms and the high oscillator strength of the JAs allow us to probe this interaction in the ultrastrong plasmon-exciton coupling regime. Linear and nonlinear optical properties of the coupled system have been measured using transient absorption spectroscopy revealing that the hybrid system shows half-plasmonic and half-excitonic properties. The tunability of the nanoprism plasmon resonance provides a flexible platform to study the dynamics of the hybrid state in a broad range of wavelengths. © 2014 AIP Publishing LLC.EnglishArticle10.1063/1.4892360