Conoscopic patterns in photonic band gap of cholesteric liquid crystal cells with twist defects

Abstract

We theoretically investigate into the effects of the incidence angles in light transmission of cholesteric liquid crystal two-layer sandwich structures with a twist defect created by rotation of the one layer about the helical axis. The conoscopic images and polarization resolved patterns are obtained for thick layers by computing the intensity and the polarization parameters as a function of the incidence angles. In addition to the defect angle induced rotation of the pictures as a whole, the rings of defect mode resonances are found to shrink to the central point and disappear as the defect twist angle varies from zero to its limiting value π/2 and beyond.

Propagation of the Ultra-Short Laser Pulses Through the Helical 1D Photonic Crystal Structure with Twist Defect

“…The light propagation through the uniform planar CLC layer in case of normal light incidence (along the helix axis that coincides with Z-axis of our coordinate system) could be simulated by exact solution of the Maxwell equations as it is shown at [5,9]. This method was proven by numerous comparisons with experimental data [5,9].…”

“…This method was proven by numerous comparisons with experimental data [5,9]. The refractive indices of the CLC were chosen as for commercially available E7 mixture (݊ = 1.72, ݊ = 1.51).…”

“…This leads to certain jump of the refractive indices modulation as it schematically shown at fig.1c. The transmission of such composite layer can be easily simulated by multiplication of 4x4 transfer matrices that corresponds to each layer as shown [9]. The introduced non-uniformity of the molecular alignment leads to appearance of the additional defect-induced Eigen modes inside the CLC layer and corresponding modification of a transmission spectrum (see fig.…”

“…In this paper we presents the first results of our theoretical investigations about the usage of artificial twist defect of helical structure of CLC [9,10] for simple laser pulse management in the case of normal light incidence onto CLC layer. We simulate the normal propagation of the bandwidth-limited ultra-short laser pulses through the planar CLC layer with twist-defect.…”

Optics of short-pitch deformed-helix ferroelectric liquid crystals: Symmetries, exceptional points, and polarization-resolved angular patterns

“…In particular, the polarization singularities such as the C points (the points where the light wave is circular polarized) and the L lines (the curves along which the polarization is linear) frequently emerge as the characteristic feature of certain polarization state distributions. For nematic and cholescteric (chiral nematic) liquid crystals, the singularity structure of the polarization-resolved angular patterns is generally found to be sensitive to both the director configuration and the polarization characteristics of incident light [15,16,21].…”