Optical properties of Heliconical Cholesterics: effects of losses and photonic density of states

Abstract

ABSTRACT The investigation of both linear and nonlinear optical properties of Heliconical Cholesteric has been triggered by the easy tuning of the Bragg resonance that can be achieved either by low-frequency electric field or by light waves. However, in previous studies two factors that can strongly affect the optical behaviour of these materials have not been considered. The first one is absorption originated by a complex dielectric permittivity at optical frequency, the second one are the modifications of the photonic density of states incurred by electrical or optical tuning of the Bragg resonance. In this paper we report an extended work of simulations addressing the mentioned issues following the same calculation method presented in previous published papers. We report first the results of the simulations performed on the optical properties of Heliconical Cholesterics showing the effects due to isotropic and anisotropic losses comparing them to what obtained in conventional cholesteric liquid crystals. Then we focus on the photonic density of states near the Bragg resonance and show that its modification when applying increasing static or optical field must be taken into account when considering laser action based on these materials since tuning may remarkably affect the lasing threshold.