液晶随机激光:原理与研究进展  

Liquid Crystal Random Laser:Principles and Research Progresses

作　　者：刘言军 蔡文锋 李烨 唐宗元 何慧琳 王家伟 罗丹 Liu Yanjun;Cai Wenfeng;Li Ye;Tang Zongyuan;He Huilin;Wang Jiawei;Luo Dan(Department of Electrical and Electronic Engineering,Southern University of Science&Technology,Shenzhen,Guangdong 518055,China)

机构地区：[1]南方科技大学电子与电气工程系,广东深圳518055

出　　处：《中国激光》2021年第12期86-104,共19页Chinese Journal of Lasers

基　　金：国家自然科学基金(62075093);深圳市科技计划(JCYJ20170817111349280,JCYJ20180305180635082,GJHZ20180928155207206);南方科技大学科研启动项目(Y01236124);南方科技大学教改项目(Y01051951)。

摘　　要：随机激光器达到阈值的方式并不是通过谐振腔,而是通过光子在增益随机散射介质中的多次散射带来的光学反馈实现的。将液晶用作散射介质,可以利用液晶易调控的特点,调整系统无序程度和染料分子的取向,使液晶随机激光器的激光阈值、强度、偏振等特性得到调控,由此可极大地拓宽随机激光器的应用范围。系统介绍了液晶随机激光器的工作原理,并分别介绍了向列相、胆甾相、蓝相和等离激元增强液晶随机激光的近期研究进展。希望能为该领域的初学者提供基础知识,同时为有经验的研究人员跟踪最新的研究进展提供重要参考。Significance A random laser necessitates not a physical resonator,but multiple scattering of photons in an active random medium to bring optical feedback to reach the threshold.This unique principle signifies that random lasers have several characteristics to distinguish them from conventional lasers.Firstly,without a resonant feedback,random lasers can be any geometries,which indicates it reduced greatly manufacturing difficulty and cost.Secondly,the emission spectrum has mutiple narrow spikes,which can be tuned by changing the pump conditions or environment.Thirdly,random lasers have low spatial coherence and large emission angle.Endowing with these superior features,random lasers have been widely used in speckle-free imaging,temperature sensing,medical diagnosis and super-resolution spectrum.After decades of development,scientists have explored a variety of materials as scattering media.Among them,liquid crystals are ideal scattering medium with a tunable disordered degree of the system and orientation of dye molecules.As a result,the laser characteristics of liquid crystal random laser,including threshold,intensity,and polarization,can be well controlled,which provides many potential opportunities for various applications of random lasers.Progress In 1968,Letokhov predicted the existence of random laser theoretically.Scattering of particles increases the distance that photons travel through the medium.The energy density of photons will increase exponentially with time as the strength of scattering and pumping energy increases.If the gain depends on wavelength,the light at this wavelength has a competitive advantage and can be further amplified to form a narrow-band spectrum,which is called spontaneous emission amplification.Meanwhile,the threshold of spontaneous emission amplification in random scattering medium is similar to that of traditional laser.Until 1994,Lawandy confirmed Letokhov′s prediction by observing narrow-band emission peaks in amplifying random medium.In 1999,the Cao′s group observed seve

关 键 词：激光器 随机激光 液晶 多重散射 漫散射 

分 类 号：O432.1[机械工程—光学工程] TN241[理学—光学]