Lasing in cholesteric liquid crystal cells with an isotropic defect layer inside

Abstract

The photonic density of states (PDS) of eigen polarizations (EPs) in cholesteric liquid crystal (CLC) cells with a defect layer inside are calculated. The dependences for the PDS and light intensity in the defect layer on the parameters characterizing absorption and gain are obtained. We investigated the possibility of connections between the PDS and the density of the light energy accumulated in the system. The influence of the defect layer and CLC layer on the PDS are investigated. It is shown that the PDS is maximum when the defect is in the center of the system. We also showed that the subject system can work as a low threshold laser, a multiposition trigger, filter, etc.

Effect of anisotropy on defect mode peculiarities in chiral liquid crystals

“…As is known, a strong accumulation of light takes place in a defective mode [12]. Dependence 2 E I  on the wavelength for incident light with diffractive circular polarization has a resonant form.…”

“…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, anyhow, 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 polarizations peculiarities and their defect modes possess polarization peculiarities, too [1][2][3][4][5][6][7][8][9][10][11][12][13].…”

“…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] and references therein) (for integrated photonics see [19,20] ).…”

A Thin‐Film Flexible Defect‐Mode Laser

“…In this configuration a separate layer is formed for the gain medium that is sandwiched between two CLC layers ( Figure ). This structure creates a defect in the macroscopic helical structure and therefore a leaky mode within the band‐gap 13–17. Furthermore, as the gain medium is de‐coupled from the CLC the device architecture allows for a wide variety of emissive compounds to be used that would not otherwise be soluble in the CLC host 18,19…”