Tunable hybrid optical modes in a bounded cholesteric liquid crystal with a twist defect

Coupling between the defect mode of a cholesteric liquid crystal and the localized mode of a cholesteric liquid crystal–phase plate–metal structure is theoretically demonstrated. It is shown that the transmittance spectrum can be tuned by changing the twist-defect angle and helix pitch, which are governed by external factors. The spectra for different circular polarizations of the incident light are different; specifically, at the nondiffracting polarization, there is no defect-mode transmittance peak.

Figure 1

Schematic of the structure. Dashed line indicates the position of the twist defect.

Figure 2

Transmittance of the structure (Fig. 1) as a function of twist-defect angle α for (a) the right- and (b) left-handed circular polarizations of incidence light. The first CLC layer is rotated and the CLC layer adjacent to the phase plate is fixed. The white dashed line shows the position of the CLC defect-mode peak calculated using formula (2) at $\alpha =1.38\mathrm{rad}$. Inset: transmittance spectrum at $\alpha =1.38\mathrm{rad}$.

Figure 3

Spatial local electric field intensity distribution in the structure from Fig. 1 for the right- and left-handed circular polarizations of incidence light at a wavelength of 649 nm and $\alpha =1.38\mathrm{rad}$.

Figure 4

Transmittance of the structure from Fig. 1 as a function of the CLC helix pitch. The white dashed line shows the position of the CLC defect-mode peak calculated using formula (2) at $\alpha =1.38\mathrm{rad}$.

Figure 5

Transmittance of the structure from Fig. 1 as a function of the twist-defect angle for the right-handed circular polarization of incidence light. The first CLC layer is rotated and the CLC layer adjacent to the phase plate is fixed. The white dashed line shows the position of the CLC defect-mode peak calculated using formula (2). $d^{\prime }=5d$.