Defect Mode in Cholesteric Liquid Crystal Consisting of Two Helicoidal Periodicities

We study a defect mode in a one-dimensional photonic band gap of a cholesteric liquid crystal (CLC) consisting of two helicoidal periodicities. The optical properties of this CLC are analyzed using 4 ×4 transfer matrix and finite difference time domain methods. One of the defect modes always appears at the band edge wavelength of the inside CLC. Furthermore, this CLC is fabricated using photopolymerized CLC films. The transmission spectrum of this CLC is observed experimentally. Some peaks appear in the one-dimensional photonic band gap of this CLC, and the experimental results agree well with the calculated ones.