Finite-Difference Time-Domain Analysis of Twist-Defect-Mode Lasing Dynamics in Cholesteric Photonic Liquid Crystal

Abstract

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.

Interval of Observation Plane in Visualization of Region near Defects in Billets Using Ultrasonic Computerized Tomography Method

“…In this simulation, we use the finite-difference time-domain (FDTD) method. [28][29][30][31][32][33][34] Figures 5 and 6 show the conditions of simulation for the spherical defect. The targets of the visualization are billets of duralumin and steel of 100 Â 100 Â 150 mm 3 .…”

Finite-difference time-domain analysis of photonic nanojets from liquid-crystal-containing microcylinder

“…1) To model the dielectric property of the LC molecules with uniaxial anisotropy, we have adopted the following dielectric permittivity tensor "ðx; yÞ. [23][24][25][26] The extraordinary and ordinary dielectric constants of LCs are ¾ e (= n e 2 ) and ¾ o (= n o 2 ), respectively, and thus, "ðx; yÞ can be represented as where ¦¾ (= ¾ e ¹ ¾ o ) is the difference between the extraordinary and ordinary dielectric constants of LCs and ª(x, y) is the angle between the major optical axis of the LC molecules (director) and the y-axis. In this study, to demonstrate the effect of introducing optical anisotropy to a PNJ, we assumed as a representative case that the LC molecules in the microcylinder show tangential alignment, in which the director of LC molecules is parallel to the LC/matrix interface and lies in the xy-plane, as schematically indicated by the dotted line in Fig.…”

Accurate transmittance analysis of liquid crystal displays using a rational fraction approach in the time domain

“…The finite-difference time-domain (FDTD) computation [1][2][3] of Maxwell's equations has been widely used as an efficient simulation tool to successfully predict lightwave propagation within liquid crystal (LC) devices [4][5][6][7][8][9]. Here, the FDTD method can simulate the complex anisotropic LCs by considering strong scattering and diffractive effects due to the rapid LC variation as well as spatial inhomogeneties of the LC director orientation, while the commonly used matrix methods are limited by specific types of geometries in modeling anisotropic structures [10,11].…”