Polarization-tunable nonlinear absorption patterns from saturated absorption to reverse saturated absorption in anisotropic GeS flake and an application of all-optical switching  

各向异性硫化锗薄片从饱和吸收到反饱和吸收的偏振可调非线性吸收模式及其在全光开关中的应用

作　　者：Hao Ouyang Chenxi Zhang Qirui Liu Siyang Hu Jun Zhang Hao Hao Jie You Xiang’ai Cheng Tian Jiang 欧阳昊;张晨希;刘祺瑞;胡思扬;张峻;郝昊;尤洁;程湘爱;江天(College of Advanced Interdisciplinary Studies,National University of Defense Technology,Changsha 410073,China;State Key Laboratory of Pulsed Power Laser Technology,Changsha 410073 China;Hunan Provincial Key Laboratory of High Energy Laser Technology,Changsha 410073,China;College of Computer,National University of Defense Technology,Changsha 410073,China 5National Innovation Institute of Defense Technology Beijing 100010,China)

机构地区：[1]College of Advanced Interdisciplinary Studies,National University of Defense Technology,Changsha 410073,China [2]State Key Laboratory of Pulsed Power Laser Technology,Changsha 410073 China [3]Hunan Provincial Key Laboratory of High Energy Laser Technology,Changsha 410073,China [4]College of Computer,National University of Defense Technology,Changsha 410073,China 5National Innovation Institute of Defense Technology Beijing 100010,China

出　　处：《Science China Materials》2020年第8期1489-1502,共14页中国科学（材料科学（英文版）

基　　金：financial support from the National Natural Science Foundation of China(11802339,11805276,61805282,61801498,11804387,and 11902358);the Scientific Researches Foundation of National University of Defense Technology(ZK16-03-59,ZK18-01-03,ZK18-03-36,and ZK18-03-22);the Natural Science Foundation of Hunan province(2016JJ1021);the Open Director Fund of State Key Laboratory of Pulsed Power Laser Technology(SKL2018ZR05);the Open Research Fund of Hunan Provincial Key Laboratory of High Energy Technology(GNJGJS03);the Opening Foundation of State Key Laboratory of Laser Interaction with Matter(SKLLIM1702);the Youth Talent Lifting Project(17-JCJQ-QT004)。

摘　　要：Due to the unique anisotropic chemical and physical properties,two-dimensional(2D)layered materials such as IV-VI monochalcogenides with puckered honeycomb structure,have received considerable interest recently.Among the IV-VI layered MX(M=Ge,Sn;X=Se,S)compounds,germanium sulfide(Ge S)stands out for its strongest anisotropic thermal conductivities and figure-of-merit values.Additionally,the layer-independent direct energy bands(Eg^1.6 e V,E1~2.1 e V)of Ge S flake provide excellent insights into further applications as visible photodetectors.Herein,the polarization-tunable nonlinear absorption(NA)patterns of Ge S flake have been systematically investigated.Specifically both the polarization-dependent Raman spectroscopy and the linear absorption(LA)spectroscopy were employed to characterize the lattice orientation and absorption edges of the251-nm Ge S flake.Considering the low damage threshold of Ge S flake,the Ge S/graphene heterostructure was fabricated to increase the threshold without changing the nonlinear properties of Ge S.Our NA results demonstrated that a 600-nm femtosecond laser with different polarizations would excite the saturated-absorption(SA)effect along armchair and reversesaturated-absorption(RSA)effect along zigzag in the Ge S/graphene heterostructure.Moreover,the function of the polarization-based Ge S/graphene heterostructure all-optical switch was experimentally verified.Notably,thanks to the polarization-dependent NA patterns(SA/RSA)of Ge S,the"ON"and"OFF"states of the all-optical switch can be accomplished by high and low transmittance states of continuous-wave laser(532 nm,80 n W),whose state can be controlled by the polarization of femtosecond switching laser(600 nm,35 fs,500 Hz,12 GW cm-2).The ON/OFF ratio can achieve up to 17%by changing polarization,compared with the ratios of 3.0%by increasing the incident power of switching light in our experiment.The polarization-tunable absorption patterns introduced in this work open up real perspectives for the next-generation optoelectronic devi近年来,一些二维层状材料,尤其是具有褶皱蜂窝结构的IV-VI族单硫化物,由于其特殊的各向异性化学和物理性质,而备受关注.在IV-VI族层状化合物MX(M=Ge,Sn;X=Se,S)中,硫化锗(GeS)以其最强的各向异性热导率和热电品质因子而引人注目.此外,GeS薄片与层数无关的直接能带(Eg^1.6 eV,E1~2.1 eV)为可见光光探测器的应用提供了良好的应用前景.本文研究了GeS薄片的偏振可调非线性吸收模式,利用偏振相关拉曼光谱和线性吸收光谱表征了厚度为251 nm GeS的晶格取向和吸收能带.考虑到GeS薄片的较低的热损伤阈值,在不改变GeS非线性特性的前提下,制备了硫化锗/石墨烯异质结.非线性吸收结果表明,在硫化锗/石墨烯异质结中,利用偏振可调的600 nm线偏振飞秒激光沿扶手椅方向激发产生饱和吸收(SA)效应,沿锯齿方向激发反饱和吸收(RSA)效应.实验验证了基于偏振的硫化锗/石墨烯异质结全光开关的功能.值得注意的是,正因为GeS的偏振相关非线性吸收模式(SA/RSA),全光开关的"开"、"关"状态可通过控制飞秒开关激光(600 nm,35 fs500 Hz,12 GW cm-2)的偏振,进而改变连续光(CW)激光(532 nm,80 nW)透射率的方式来实现.通过改变开关光的偏振,开关比可以达到17%,与之相比,通过提高开关光入射功率获得的开关比仅为3.0%.本文介绍的偏振可调吸收模式,为基于硫化锗/石墨烯异质结的下一代光电子器件开辟了新的前景.

关 键 词：polarization-tunable NA I-scan all-optical switch modulated depth 

分 类 号：TN249[电子电信—物理电子学] TQ134.31[化学工程—无机化工]