We have numerically investigated lasing dynamics in cholesteric liquid crystal (CLC) with gain by an auxiliary differential equation finite-difference time-domain (ADE-FDTD) method in which the FDTD method is coupled with a rate equation in a four-level energy structure. Circularly polarized lasing was achieved at the photonic band edge above threshold pumping. Our model opens a way for a computational design of the CLC laser on the basis of numerical simulation to realize a more efficient device architecture for a greatly reduced lasing threshold, which is still under extensive study.

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We have numerically investigated lasing dynamics from a twist defect in a cholesteric liquid crystal (CLC) by an auxiliary differential equation finite-difference time-domain (ADE-FDTD) method. As ADEs, the equation of motion of polarization described on the basis of the classical electron oscillator (Lorenz) model and the rate equation in a four-level energy structure are incorporated. A lower lasing threshold has been obtained from the twist-defect mode (TDM) than from band-edge lasing. Standing-wave-like electric fields are strongly localized only in the vicinity where a twist defect is introduced into a CLC, which works as a distributed feedback TDM laser source. The oscillation direction of a standing-wave electric field is not parallel or perpendicular to LC molecules, which is quite different from the bulk CLC case. Our results may be useful for creating more efficient TDM-based CLC lasers.

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