Absorption and emission in defective cholesteric liquid crystal cells

Abstract

We investigated peculiarities of absorption, emission and photonic density of states of a cholesteric liquid crystal with an isotropic defect inside. The influence of the defect position on absorption and emission in the system was studied. It is shown that for non-diffracting circularly polarized incident light absorption/emission is maximum if the defect is in the centre of the system; and for diffracting circularly polarized incident light absorption/emission is maximum if the defect is shifted from the centre of the system to its left border from where light is incident. We also investigated influence of the defect layer thickness and those parameters which characterize absorption and gain on absorption and emission. The influence of anisotropic absorption in the cholesteric liquid crystal layer on photonic states of density was investigated, too.

Effect of anisotropy on defect mode peculiarities in chiral liquid crystals

“…Let us only note that although it is impossible to ascribe a direct physical meaning to the PDS in equation ( 1) in a general case, it can be used as a parameter, which can provide some heuristic guidance in experiments for the PDS dispersionrelated effects. Moreover, as was shown in [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], equation ( 1) is applicable for finite PCs layers, even for cases with absorption and amplification (naturally, for weak ones).…”

“…The well-known representatives of soft PCs are cholesteric liquid crystals (CLCs) and blue phases of liquid crystals. CLC layers as PCs have polarization peculiarities and their defect modes possess polarization peculiarities too [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Recently, there has been a great deal of activity in the field of localized optical modes, edge modes and defect modes in CLCs due to the possibility of reaching lasing in CLCs.…”

“…In the general case, lasers on the base of CLC layers can be separated into three classes: (1) lasers working on edge modes; (2) lasers on defect modes; and (3) random lasers. Cholesteric LCs with defects of different types have been studied in the last decades to gain insight into the specific features of lasing on defect modes, characteristics of absorption/emission on these modes, etc (see [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and references therein; for integrated photonics see [15][16][17][18][19][20]).…”

Near-IR unidirectional absorption in a tunable asymmetric one-dimensional photonic crystal with VO2 defect layers

“…In the process of research and improvement of PC, researchers are more eager to master more approaches to adjust the spectral properties, among which achieving dynamic control of electromagnetic propagation is a popular area. The ability to change the optical properties by external stimuli without destroying the structure is exciting, mainly by combining the designed structures with active media (liquid crystal [10,11], graphene [12], phase change materials [13,14], etc.). Phase change materials have received greater attention in this challenge because they can spontaneously generate fast and reversible modulation through various stimuli, resulting in inconsistent spectral responses [15,16].…”

Multimode Robust Lasing in a Dye-Doped Polymer Layer Embedded in a Wedge-Shaped Cholesteric

“…Furthermore, layered constructions give a chance to obtain multimode lasing in the broad visible spectral range due to the observed defect modes. The defect mode features depend on the position of the defect layer which influences the PBG width as well [ 25 ].…”