基于液晶光控取向技术实现光场调控

发布时间：2018-01-01 14:20

本文关键词：基于液晶光控取向技术实现光场调控　出处：《南京大学》2017年博士论文　论文类型：学位论文

【摘要】：近年来,随着激光技术的不断进步和光学领域的日益发展,光场调控受到越来越多的关注。一方面,通过对高斯光束的位相和振幅等参数的调控,可分别产生涡旋光束和艾里光束等一些结构新颖、性质独特的光场,它们被广泛应用于光学操控、量子计算与存储、天文观测、高分辨显微成像等领域。另一方面,通过对入射光偏振信息的调控来实现光场的退偏,在光纤通讯及光学探测等方面也起着举足轻重的作用。液晶凭借其优异的电光特性,可用来实现对光场的高效调控。作为新兴的取向液晶方式,光控取向技术在制备复杂结构的液晶元件方面表现出巨大的优势。本文采用基于SD1的液晶光控取向技术,结合自主研发的数字微镜器件微缩投影曝光系统,设计并制备了用于光场调控的各类液晶元件,主要的研究成果如下:1.首次通过对液晶方位角的控制,制备了不同取向模式及不同结构的液晶叉形光栅,实现了一系列涡旋光束的产生与调控。其中,混合排列型液晶叉形光栅可实现由高斯光到±1级衍射涡旋光束74%的高转换效率,并可在低电压1.7 V和15 V的条件下完成涡旋光束的开关调控。通过优化此液晶元件的参数,分别获得了 300μs和570μs的快速开关响应时间。此液晶叉形光栅对入射光偏振无依赖,且宽波段适用,SD1的可擦写特性额外赋予了涡旋光束可重构的功能。这些优势增加了对涡旋光束调控的灵活性,拓展了涡旋光束的应用前景。2.在传统立方位相模板的基础上,引入几何位相的概念,采用部分重叠分步曝光的方式,制备了分子指向矢空间渐变的液晶偏振艾里模板,加以透镜进行傅里叶光学变换,完成了高斯光束到单/双艾里光束的调控。通过调节入射光的偏振态,实现了两支艾里光束之间的相互切换,且可同时控制它们光场能量的任意占比。通过测试双支艾里光束的传播动态,验证了其横向自加速和无衍射的性质。此液晶偏振艾里模板宽波段适用,且可以承受至少600脉冲(0.5J/cm2,1064 nm,10ns,1Hz)的强光照射,为高质量、多功能艾里光束的产生与调控提供了一个便捷有效的途径。3.通过引入q波片产生涡旋光的技术,结合液晶偏振艾里模板,对高斯光的位相和振幅同时进行了调控,产生出了不同模式的涡旋艾里光束。分析了涡旋艾里光的传播动态,从实验上验证了此复合光场中涡旋光的拓扑荷、无衍射、自愈和横向自加速等性质。借助外加电场的调节或光路中四分之一波片的旋转,轻易地获得了高斯光、涡旋光、矢量光、艾里光以及它们结合光场之间的相互转换,为光场调控和光束整形提供了一个灵活高效的方式。高质量涡旋艾里光束的产生与自愈、类无衍射和横向自加速涡旋光束的提出,为它们在多方位的微粒操控、量子通讯的无损传输、更高清的生物显微观测等方面的应用做了很好的铺垫。4.基于半波片对线偏振光的调制机理,采用分步曝光的方式,制备了一个新型的液晶退偏器。它由24 × 18个液晶分子指向矢随机平行排列的方形微区构成,在无需外加电场的情况下便可对通讯波段任意方向入射的线偏振光源实现偏振度小于5%的退偏效果,展现了很好的偏振不敏感特性。对于圆偏振和椭圆偏振入射光,通过对样品加电调节其位相延迟量也可以达到同样的退偏功能。此退偏器不仅适用于单波长1550 nm的光源,而且对1520 nm-1610 nm的宽波段复色光源亦起到了很好的消偏作用,得到出射光场最小偏振度的值分别仅为0.384%和0.156%。此液晶退偏器综合性能优于商业产品,在激光加工、天文学仪器、光纤通讯等光电系统中有很大的应用价值。
[Abstract]:In recent years, with the development and progress of the optical field of laser technology, optical field control has attracted more and more attention. On the one hand, through the regulation of the Gauss beam amplitude and phase parameters, respectively generated vortex beam and Airy beam and some novel structure and unique properties of light, they are application in optical manipulation, quantum computing and storage, astronomical observation, high resolution imaging and other fields. On the other hand, through the regulation of the polarization of the incident light information to realize the depolarization of the light field, it also plays an important role in optical communication and optical detection and other aspects. The liquid crystal with its excellent electro-optical properties. Can be used to achieve efficient control of light field. As the orientation of the liquid crystal emerging, photoalignment technology in the preparation of the complex structure of the liquid crystal element showed great advantages. This paper uses liquid crystal light based on SD1 Orientation control technology, combined with independent research and development of digital micromirror device projection exposure system, was designed and prepared for light field control of liquid crystal element, the main results are as follows: 1. for the first time by controlling the liquid crystal orientation angle, different orientation mode and different structure of the liquid crystal fork shaped grating prepared, have realized with the regulation of a series of vortex beams. The hybrid alignment type liquid crystal grating with high conversion efficiency can be forked by Gauss to + 1 level diffraction optical vortex beam 74%, and can complete the switch to control the vortex beam in the low voltage of 1.7 V and 15 V conditions. By optimizing the parameter of the liquid crystal element, respectively. The fast switching of 300 s and 570 s. The response time of the liquid crystal grating forked no dependence on the polarization of the incident light, and wide band application, SD1 rewritable characteristics given additional vortex beam reconfigurable function. These advantages The potential increase of vortex beam control flexibility, expand the application prospect of.2. vortex beam based on traditional cubic phase template, introducing the concept of geometric phase, the overlapping step exposure mode, liquid crystal polarization AI molecular director in spatial gradient template preparation to lens Fourier optical transform, complete Gauss beam to single / double Airy beam regulation. Through adjusting the incident light polarization state, to achieve the two branches between Airy beams are switched, and can also control their light field of arbitrary proportion. Through the test of double Airy beam propagation dynamics, verify the properties of self acceleration and the transverse diffraction. Application of the liquid crystal polarization Elliot template wide band, and can withstand at least 600 pulse (0.5J/cm21064 nm, 10ns, 1Hz) the glare, high quality, multi-function Airy beam generation and regulation Provides a convenient and effective way to produce.3. by introducing Q wave vortex technology, combined with the liquid crystal polarization Elliot template, phase and amplitude of the light of Gauss at the same time the regulation has produced different patterns in AI vortex beam. We analyzed the spreading dynamic optical vortex AI, it is verified experimentally this topology composite optical field in the vortex charge, non diffraction, self-healing and self accelerating transverse properties. By means of external rotation or a wave of four points in the optical path of the film field, easily won the Gauss vortex light, light, light vector, and their combination of AI optical conversion between the optical field. It provides a flexible and efficient way for the light field regulation and beam shaping. The high quality vortex Airy beam generation and self-healing, non diffraction and self accelerating transverse vortex beam is proposed, they are manipulating particles multi-faceted, quantum communication without The transmission loss, more HD and other aspects of the application of biological microscope to pave the way for.4. good modulation mechanism of half wave plate of linearly polarized light based on step by step exposure mode, the preparation of a new type of liquid crystal depolarizer. It consists of 24 x 18 liquid crystal molecules to square vector random parallel arrangement the micro area composition, without external electric field under the condition of linear polarization light source is incident on the communication band in any direction to achieve depolarization polarization degree is less than 5%, showing good polarization insensitive characteristics. For elliptical and circular polarization of incident light, the sample power adjusting the phase delay quantity can achieve the same function. Partial back light source of the depolarizer is not only suitable for the single wavelength of 1550 nm, and 1520 nm-1610 nm wide band of polychromatic source also played a partial effect very good, get a light reflecting field minimum polarization values were only For 0.384% and 0.156%., the performance of the liquid crystal depolarizer is better than that of commercial products. It has great application value in laser processing, astronomical instruments, optical fiber communication and other optoelectronic systems.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O753.2

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