Lee Sang Seok, Kim Jong Bin, Kim Yun Ho, Kim Shin-Hyun
Department of Chemical and Biomolecular Engineering (BK21 Plus Program), Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
Advanced Materials Division, Korea Research Institute of Chemical Technology, Daejeon 34114, Republic of Korea.
Sci Adv. 2018 Jun 22;4(6):eaat8276. doi: 10.1126/sciadv.aat8276. eCollection 2018 Jun.
Cholesteric liquid crystals (CLCs) have a photonic bandgap due to the periodic change of refractive index along their helical axes. The CLCs containing optical gain have served as band-edge lasing resonators. In particular, CLCs in a granular format provide omnidirectional lasing, which are promising as a point light source. However, there is no platform that simultaneously achieves high stability in air and wavelength tunability. We encapsulate CLCs with double shells to design a capsule-type laser resonator. The fluidic CLCs are fully enclosed by an aqueous inner shell that promotes the planar alignment of LC molecules along the interface. The outer shell made of silicone elastomer protects the CLC core and the inner shell from the surroundings. Therefore, the helical axes of the CLCs are radially oriented within the capsules, which provide a stable omnidirectional lasing in the air. At the same time, the fluidic CLCs enable the fine-tuning of lasing wavelength with temperature. The capsules retain their double-shell structure during the dynamic deformation. Therefore, the CLCs in the core maintain the planar alignment along the deformed interface, and a lasing direction can be varied from omnidirectional to bi- or multidirectional, depending on the shape of deformed capsules.
胆甾相液晶（CLCs）由于其沿螺旋轴方向折射率的周期性变化而具有光子带隙。含有光学增益的胆甾相液晶已被用作带边激光谐振器。特别是，颗粒状的胆甾相液晶可实现全向激光发射，有望成为一种点光源。然而，目前还没有一个平台能够同时实现空气中的高稳定性和波长可调性。我们用双层壳封装胆甾相液晶，设计出一种胶囊型激光谐振器。流动的胆甾相液晶被内层水壳完全包围，该水壳促进液晶分子沿界面的平面排列。由硅橡胶制成的外壳保护胆甾相液晶核心和内壳不受周围环境影响。因此，胆甾相液晶的螺旋轴在胶囊内呈径向排列，从而在空气中提供稳定的全向激光发射。同时，流动的胆甾相液晶能够随温度对激光波长进行微调。在动态变形过程中，胶囊保持其双层壳结构。因此，核心中的胆甾相液晶沿变形界面保持平面排列，根据变形胶囊的形状，激光发射方向可以从全向变为双向或多向。
