Observations of cavity polaritons in one-dimensional photonic crystals containing a liquid-crystalline semiconductor based on perylene bisimide units

We investigated the optical transmission properties of one-dimensional photonic crystal (1D-PC) microcavity structures containing the liquid-crystalline (LC) perylene tetracarboxylic bisimide (PTCBI) derivative. We fabricated the microcavity structures for this study by two different methods and observed the cavity polaritons successfully in both samples. For one sample, since the PTCBI molecules were aligned in the cavity layer of the 1D-PC by utilizing a friction transfer method, vacuum Rabi splitting energy was strongly dependent on the polarization of the incident light produced by the peculiar optical features of the LC organic semiconductor. For the other sample, we did not utilize the friction transfer method and did not observe such polarization dependence. However, we did observe a relatively large Rabi splitting energy of 187 meV, probably due to the improvement of optical confinement effect.

Figure 1

(a) Chemical structure of PTCBI with four 1,1,1,3,3-pentamethyldisiloxane chains. (b) Relationship between the rubbing direction and the lamination direction of the columnar layer.

Figure 2

Polarizing optical micrographs of uniaxially ordered LC PTCBI derivative on the substrate performed to the rubbing treatment. Here, P and A are optical axis direction of polarizer and analyzer. Dashed arrow C indicated the columnar axis direction. Since this sample was well aligned with large area of several hundred microns order, one can see that the color of entire image greatly changed owing to the birefringence of the liquid crystal when the angle of C with respect to P was changed from (a) $0^{\circ }$ to (b) ${45}^{\circ }$.

Figure 3

Absorption spectra of the chloroform solution of the PTCBI derivative (dashed line) and the LC PTCBI film (solid line) at room temperature.

Figure 4

Polarization dependence of absorption spectra of the LC PTCBI film at room temperature.

Figure 5

Incident position dependence of the transmission spectra of cavity A at room temperature. Here, the polarization angle was set to ${90}^{\circ }$.

Figure 6

The incident-position dependence of the energy of the transmission peak of cavity A corresponds to the dispersion curve of the cavity polariton. The open and closed circles show the dispersion curves with the polarization angle set to ${90}^{\circ }$ and $0^{\circ }$, respectively. The solid and dashed lines are the fitting curves described in Eq. (1).

Figure 7

Polarization dependence of the transmission spectra of cavity A at room temperature.

Figure 8

Incident position dependence of the transmission spectra of cavity B at room temperature.

Figure 9

The Incident position dependence of the energy of the transmission peak of cavity B corresponds to the dispersion curve of the cavity polariton. The open circles are the dispersion curves and the solid lines are the fitting curves.