Abnormal behavior of optical signal transfer in pi-conjugated organic microplates and focused electron-beam-treated nanorods

Abstract

We observe abnormal behavior in Raman and photoluminescence (PL) signal transfer, i.e., waveguiding in pi-conjugated organic 1,4-bis(3,5-bis(trifluoromethyl) cyanostyryl)-2,5-dibromobenzene (CN-TSDB) microplates (MPs) and focused electron-beam-treated rubrene nanorods (NRs). In diamond-shaped CN-TSDB MPs, the intensities of the waveguided output Raman characteristic peaks decrease exponentially while approaching the center of the sample, but increased drastically thereafter. Similar abnormal behavior is also observed for the output PL intensities of the CN-TSDB MPs. For one-dimensional rubrene NRs, the PL waveguiding characteristics are improved when using an indium tin oxide (ITO) glass substrate and an oil objective lens, compared to a SiO2 substrate and an air gap lens. We also observe abnormal behavior in PL waveguiding, such as an abrupt enhancement of the waveguiding efficiency at the point of electron-beam treatment in the rubrene NRs. These results can be analyzed in terms of geometrically constructive interference of optical path in the CN-TSDB MPs, and of the local variation in the molecular ordering of the rubrene NRs resulting from the focused electron-beam irradiation. (C) 2015 Elsevier B.V. All rights reserved