Fig. 5

(a) Reflectivity spectra for the glass/TDBC-PVA (35 nm)/Ag (60 nm/Air structure (shown as an inset to figure (b)), inverted with respect to that of Fig. 2 with the same thicknesses of the Ag and TDBC-PVA layers as those of sample 1, calculated by FDTD, plotted versus the energy of the incident light. The spectra are arbitrarily shifted for clarity and the incidence angles are indicated. A sharp and broad dip occur for each incidence angle. The sharp dip, which corresponds to the SPR mode, see e.g. the spectrum at \(\:\theta\:=42^\circ\:\) corresponding to excitation at 1.95 eV (632.8 nm) and angular reflectivity scan (b), spans through the broad one, which remains at the same energy position, i.e. 2.1 eV corresponding to the excitonic transition of TDBC, when the angle is changed, and moves to larger angles for larger energies. (c) Energies of reflectivity minima versus the wavevector for this structure. Open and full circle scatters correspond to the energies of the exciton and plasmon resonances, respectively; and the dashed horizontal lines correspond to the energies of the 632.8 nm (1.95 eV) excitation laser (red) and TDBC absorption maximum 590 nm (2.1 eV) (black). FDTD calculations of (b) the angular reflectivity scan and (d) the electric field distribution at the structure for 632.8 nm light excitation. The color scale indicates the amplitude of electric field normalized by the amplitude of the incident electric field.