Optical Properties of a One-Dimensional Photonic Crystal Containing a Twisted Nematic Liquid Crystal Defect Layer

Abstract

We analyze the optical properties of a one-dimensional photonic crystal containing a twisted nematic liquid crystal (NLC) defect layer. For randomly polarized light incidence, two photonic defect modes were found to appear in the photonic band gap of the one-dimensional photonic crystal, and were associated either with the molecular long axis experiencing the averaged extraordinary refractive index or the molecular short axis experiencing the averaged ordinary refractive index, of the defect NLC layer. Numerical analyses also revealed that the transmitted light at the defect mode is linearly-polarized light at an angle which is determined both from the twist angle of the twisted NLC and the resulting optical rotatory power. When the thickness of the defect layer is sufficiently thin, optical rotation can be ignored and the output polarization angle is at half the twist angle for the long axis mode and at 90 degrees to that for the short axis mode.