构建于SU8光栅的精密波长调谐胆甾相液晶激光器研究

A cholesteric liquid crystal was known as self-organized photonic crystal. Because it’s planar alignment state and it has a photonic band gap. A photonic band gap edge lasing could be obtained by cholesteric liquid crystal mixing a laser dye upon a pumping laser. And the lasing wavelength will be tuned by the field of magnetic, temperature, stress, electric and light. Because of the advantages of without resonator, small size, simple structure, low cost and widely tunable range, cholesteric liquid crystal laser shows a extensive prospect for laser display, optical communication, photon integration and biomedical engineering fields application. In the traditional cholesteric liquid crystal laser, the laser emission intensity was not strong enough and the lasing emission was directed vertically along the glass substrate plane. In addition, to achieve a precision tuning wavelength lasing by using the tuning mode of magnetic, temperature, stress and light, a more precision attachment was needed. It will make laser structure more complex and more expensive. In this project application, a cholesteric liquid crystal laser built on the SU8 grating is proposed. Each channel in the grating as a separately laser resonator, which will increase the lasing emission intensity greatly. The liquid crystal molecules helix align along the parallel to the glass substrate plane, the lateral lasing emission is achieved, it is beneficial to device integration. When electrostatic fields were applied to the ITO electrode of the glass substrate, the helix alignment of liquid crystal will shrink gradually and a precise continuous wavelength tuning will achieved. The SU8 grating region is divided into three parts and filled with the red, green, blue three primary mixture of laser dye and cholesteric liquid crystal respectively. A multi-color lasing will be achieved in one device.

平面态排列的胆甾相液晶被誉为自组装一维光子晶体,具有光子禁带。液晶中掺杂激光染料, 在一定抽运光的作用下, 光子禁带边沿出现激光辐射。可通过外场改变液晶分子取向,调谐输出激光波长。具有无需谐振腔，尺寸小、易获得、结构简单、成本低、调谐范围宽等优点。在光显示、光通讯、光子集成和生物医学工程等领域有广泛的应用前景。传统胆甾相液晶激光器，出射激光垂直玻璃基板方向，出射激光强度有限。磁场、温度、应力、光场等调谐方式，精密调谐激光波长，需其它精密附件。本项目提出将胆甾相液晶激光器构建在SU8光栅中。光栅中每一通道为一独立的激光谐振腔，将大幅度提高出射激光强度。液晶分子沿平行玻璃基板平面螺旋排列，器件侧面出射激光，有利于器件集成化。利用玻璃基板的ITO电极施加电场，使分子螺距逐渐收缩，达到精密连续波长调谐。SU8光栅划分为三个区域，分别填充红、绿、蓝三基色胆甾相液晶激光混合物，同一器件中实现多色输出。

本项目面向传统液晶盒结构胆甾相液晶激光器的出射激光垂直玻璃基板方向，出射激光强度有限的问题，将胆甾相液晶激光构建在SU8光栅中，探索器件最佳工艺条件，在器件侧面获得了较强的随机激光及单模激光输出，有利于将器件复合到集成光学系统中使用。设计制作了指纹织构胆甾相液晶激光器，探索器件制备工艺条件，实现了器件侧面电场调谐波长的单模激光输出，解决以往胆甾相液晶的螺距需要限制在纳米量级以匹配激光染料荧光发射光谱的问题，拓宽了应用范围。比较研究了传统液晶盒结构、SU8光栅结构的一维载体和光子晶体光纤二维载体中的液晶随机激光。对以上不同结构器件中，液晶激光产生和传输机制进行了深入分析，进一步充实了液晶激光理论。研究结果对胆甾相液晶激光器在集成光学、光传感、光化学等领域的应用提供了重要的技术参考。