Lasing peculiarities in cholesteric multilayer structure with dye-doped polymer film depending on the concentration of laser dye and pumping energy

We have experimentally investigated lasing peculiarities in a cholesteric liquid crystal - dye-doped polymer layer - cholesteric liquid crystal three-layer wedge-cell system with different laser dye concentration changing pumping energy. It was theoretically and experimentally shown that there are photonic defect modes in cholesteric photonic bandgap of the wedge-cell system. The problem was solved by Ambartsumian's layer addition modified method. It was shown that in the mentioned above system it is possible to obtain lasing generation and it should be noted that in our case the observed lasing peculiarities are not because of the isotropic defect (planar polymer layer) but the observed features are due to the cholesterics, namely by changing the thickness of the layer of cholesterics, we are able to ensure a change in the laser wavelength, due to the pitch jumps and therefore helix pitch gradient. The advantage of our experiment is the continuous change in the thickness of the cholesteric liquid crystal layer. To prevent degradation of the molecules, decrease of the fluorescence output as well as to except convective flows for higher pumping energies the dye concentration in the polymer was chosen 10(-4)mol/l. We have experimentally shown the dependences of the intensity and displacement of the lasing peaks' on the pumping power.