Observation of cavity polaritons in a metal-mirror Fabry-Pérot microcavity containing liquid-crystalline semiconductor based on perylene bisimide units

We investigate the optical properties of a metal-mirror microcavity containing a liquid-crystalline (LC) perylene tetracarboxylic bisimide (PTCBI) derivative. Measurements of the transmission's incidence angle dependence show that the peaks are split in a complex way and shift as the angle changes. Further, measurements of the photoluminescence spectrum's emission angle dependence show that the peak also shifts with the angle, as in the transmission experiment. We also carry out a theoretical analysis; the theoretical and experimental results are in very good agreement, and we estimate the vacuum Rabi splitting energies to be about 212, 180, and 240 meV. In addition, the peak photoluminescence energy coincides with the lower polariton branch obtained by transmission experiment. Finally, in a time-resolved photoluminescence experiment, we observe a fast relaxation component that is not seen in the bare LC PTCBI film. We believe this is due to cavity effects increasing the spontaneous emission transition rate, indicating that the emissions are due to cavity polaritons.

Figure 1

Chemical structure of PTCBI with four 1,1,1,3,3-pentamethyldisiloxane chains.

Figure 2

Absorption spectrum (solid line) and photoluminescence spectrum (dashed line) of the LC PTCBI film at room temperature.

Figure 3

Dependence of the transmission spectrum on the incidence angle (solid lines). The dotted lines show the peak absorption energies of a bare LC PTCBI thin film.

Figure 4

Dependence of the photoluminescence spectrum (solid lines) on the emission angle.

Figure 5

Dispersion curves for the cavity polaritons, calculated using the coupled harmonic oscillator Hamiltonian (solid lines). The open and closed circles plot the energies of the transmission and photoluminescence peaks, respectively, as a function of angle.

Figure 6

Photoluminescence decay curves of three types of thin LC PTCBI films, namely, (a) a thin PTCBI film spin coated onto a glass substrate (solid line), (b) a thin silver film deposited onto a glass substrate and then spin coated with a thin PTCBI film (broken line), and (c) a thin silver film deposited on a thin spin-coated PTCBI film on a substrate (dotted line).

Figure 7

Photoluminescence decay curves of the microcavity structure, at emission angles of (a) 0° (solid line), (b) 20° (broken line), and (c) 40° (dotted line).