Abstract
Cholesteric liquid crystals (CLCs) with induced defects are one of the most prominent materials to realize compact, low-threshold and tunable coherent light sources. In this context, the investigation of optical properties of induced defect modes in such CLCs is of great interest. In particular, many studies have been devoted to the spectral control of the defect modes depending on their thickness, optical properties, distribution along the CLC, etc. In this paper, we investigate the lasing possibilities of a dye-doped polymer layer embedded in a wedge-shaped CLC. We show that multimode laser generation is possible due to the observed multiple defect modes in the PBG that enlarges the application range of the system. Furthermore, our simulations based on a Berreman 4 × 4 matrix approach for a wide range of CLC thickness show both periodic and continuous generation of defect modes along particular spectral lines inside the PBG. Such a robust spectral behaviour of induced defect modes is unique, and, to our knowledge, is not observed in similar CLC-based structures.
Highlights
Accepted: 30 August 2021Recently, special attention has been paid to the study of the optical properties of photonic structures (PS), based on liquid crystals (LC) [1]
We have investigated the transmission properties of circularly polarized light in the above-mentioned layer and show that our layer is optically isotropic since the transmission coefficient for right (RCP) and left (LCP) circularly polarized light is almost the same, see Figure 4b
We modelled a system consisted in an isotropic dielectric layer embedded in two thick Cholesteric liquid crystals (CLCs) layers (CLC-IDL system), where the thicknesses of the CLC layers can be changed, see Figure 9a
Summary
Accepted: 30 August 2021Recently, special attention has been paid to the study of the optical properties of photonic structures (PS), based on liquid crystals (LC) [1]. Cholesteric liquid crystals (CLC) are the most well-known representatives of 1D chiral PSs with local positive optical anisotropy and helical distribution of the director field [4] Another important feature of CLC is the geometric phase which is the basis of the realization of flat mirror enabling the broadband generation of optical vortices upon reflection [5]. These materials self-organize their periodic structure and form a photonic bandgap (PBG) where circularly polarized light with the same handedness as that of the CLC helix cannot propagate [6]. Several studies on chiral photonic crystals have shown that it is possible to create localized optical modes within the PBG by inducing a defect into the periodic structure [7,8,9,10,11,12,13,14,15]
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