Emission light from prism/silver/rhodamine-B LB film and multiple surface plasmon excitations in the ATR Kretschmann configuration

Emission light through the prism in the Kretschmann configuration of prism/Ag thin film/rhodamine-B (RB) Langmuir–Blodgett (LB) film has been observed by means of direct irradiation of a laser beam from air to the RB LB film, that is, the reverse irradiation method against the conventional attenuated total reflection (ATR) method. The emission light intensities and the spectra strongly depended upon the emission angle at the prism. The relation between the peak wavelengths of the spectra and the emission angles corresponded to the dispersion property of the resonant excitations of surface plasmons (SPs) in the ATR configuration. It was concluded that the emission light was caused by multiple excitations of SPs in the ATR configuration. Emission light through the prism was also observed below the reflection angle of the resonant one when the SP was resonantly excited in the conventional ATR measurement. This emission light also showed the same property as the one in the reverse irradiation method. It is thought that the phenomenon will be used as a new sensing device.