Photonic density of states of cholesteric liquid crystal cells

Abstract

The photonic density of states (PDS) of the eigen polarizations (EPs) in cholesteric liquid crystal (CLC) cells are calculated. The exact analytic expressions for the reflection and transmission matrices for the finite thickness CLC layer are used. We obtained the dependences for the PDS on the parameters characterizing absorption and gain, as well as the CLC cell thickness, CLC local dielectric anisotropy and refractive index of CLC layer surrounding. The possibility of connections between the PDS and the density of the light energy accumulated in the medium are investigated and it was shown that these characteristics have analogous spectra and, besides, the influences of the problem parameters on these characteristics also were analogous. We have shown, that the decrement of the refractive index of CLC layer surroundings leads to a sharp increase of the maximum PDS and, consequently, leads to a sharp decrement of the laser excitation threshold. The PDS dependence on the refraction coefficients of the substrates of the Fabry-Perot resonator filled with a CLC planar layer was investigated, too. It is shown that the subject system can work as a low threshold laser or a multi-position trigger.

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

“…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 dispersion-related effects. Moreover, as was shown in [9][10][11][12], equation ( 1) is applicable for finite PCs layers, even for cases with absorption and amplification (naturally, for weak ones).…”

“…The possibilities of decreasing the lasing threshold in CLCs and multilayer systems with CLC layers have been studied both theoretically [5][6][7] and experimentally [8]. In the following three papers [9][10][11] the effect of loss and gain on the PDS was reported. Dolganov reported in [12] that a highly sensitive method was used to determine the PDS, as well as a drastic increase in the PDS near the PBG borders, and oscillations related to Pendellösung beatings were observed.…”

Absorption and emission in defective cholesteric liquid crystal cells

“…( 2), anyhow, it can be used as a parameter providing some heuristic guidance in experiments for the PDS dispersion-related effects. Moreover, as it was showed in [28][29][30][31] Eq. ( 2) is applicable for finite PCs layers, even for the cases with absorption and amplification (naturally, for weak ones).…”

Cone-Shaped Emissions in Cholesteric Liquid Crystal Lasers: The Role of Anomalous Scattering in Photonic Structures

“…The topic of DOS at normal and oblique incidences in systems with anisotropic gain has been also studied in refs − .…”