Abstract

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 10⁻⁴mol/l. We have experimentally shown the dependences of the intensity and displacement of the lasing peaks’ on the pumping power.

摘要

我们已经通过实验研究了胆甾醇型液晶–染料掺杂的聚合物层–胆甾醇型液晶三层楔形单元系统中的激光特性，其中激光染料的浓度改变了泵浦能量。理论和实验表明，楔形单元系统的胆甾型光子带隙中存在光子缺陷模式。通过Ambartsumian的图层加法修改方法解决了该问题。结果表明，在上述系统中有可能产生激光，并且应该注意，在我们的情况下，观察到的激光特性不是由于各向同性缺陷（平面聚合物层）引起的，而是观察到的特征是由于胆甾醇型引起的。 ，即通过更改胆甾醇层的厚度，我们可以确保改变激光波长，由于螺距跳变，因此螺旋螺距梯度。我们实验的优点是胆甾型液晶层厚度的连续变化。为防止分子降解，选择了荧光输出降低以及为了提高泵浦能量而采用对流以外的方法，选择了聚合物中的染料浓度10^-4 mol / l。我们已经通过实验证明了激光峰的强度和位移对泵浦功率的依赖性。