The photonic density of states and the light energy density in 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 dependences of the PDS on the parameters characterizing absorption, gain and refractive index of the CLC layer surroundings were obtained. We investigated the possibility of connections between the PDS and the density of the light energy accumulated in the medium and showed that these characteristics have analogous spectra and, besides, the influences of the problem parameters on these characteristics also are analogous. It was shown that the decrement of the refractive index of the CLC layer surroundings leads to a sharp increase of the maximum PDS and, consequently, leads to a sharp decrement of the laser excitation threshold. We showed that the subject system can work as a low threshold laser or a multi-position trigger.

Wavelength-tunable and shape-reconfigurable photonic capsule resonators containing cholesteric liquid crystals

“…In a photonic stop band, a circularly polarized light of the same handedness to the CLC structure is selectively reflected due to low-photon density of states (DOS) ( 3 ). The photon DOS sharply increases in band edges, which enables the use of CLCs as mirrorless laser resonators ( 4 , 5 ). When light emitters, such as fluorescent dyes and quantum dots, are present in the CLCs, their emission spectra are markedly modulated.…”

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).…”

Responsive Liquid‐Crystal Microlaser Arrays with Tactile Perception

“…Note that the PL spectra are modulated by the CLC photonic bandgap due to the large densities of photonic states near photonic bandedges (Figure S14, Supporting Information). [ 41 ] With increasing pump fluence, a sharp PL peak appears near the CLC photonic bandedge accompanied by a dramatical increase of PL intensity, which reveals the bandedge laser generation. [ 42,43 ] Besides, the corresponding PL intensity and full‐width at half‐maximum (FWHM) as a function of pump fluence exhibit clear knee behavior characteristics at a threshold of ≈25.6 µJ cm −2 (Figure 3c), confirming the lasing action in the CLC microlaser unit.…”