Behavior of the Cholesteric Liquid-Crystal Fabry-Perot Cavity in the Bragg Reflection Band

In this Letter, we investigate the behavior of the cholesteric liquid-crystal Fabry-Perot cavity in the spectral range of the Bragg reflection band. We show that in this region the $2\times 2-\mathrm{Jones}-\mathrm{matrix}$ calculation gives a false predication. However, by the use of the $4\times 4-\mathrm{matrix}$ method, interesting features are revealed in the resonance spectra. The resonance spectra split when $\lambda \sim \overline{n}P$. Our experiments confirm this phenomenon. The experimental results show that the splitting occurs in a steplike fashion. This can be explained by the quantization of the pitch that occurs due to the fixed boundary conditions.