WS_(2)纳米薄膜厚度依赖的三阶非线性吸收特性研究  

Thickness-dependent Third-order Nonlinear Optical Absorption of WS_(2) Nanofilms

作　　者：靳延平 卢春辉 赵奇一 徐新龙 JIN Yanping;LU Chunhui;ZHAO Qiyi;XU Xinlong(School of Physics,Northwest University,Xi'an 710127,China;School of Science,Xi'an University of Posts&Telecommunications,Xi'an 710121,China)

机构地区：[1]西北大学物理学院光子学与光子技术研究所,西安710069 [2]西安邮电大学理学院,西安710121

出　　处：《光子学报》2022年第4期417-423,共7页Acta Photonica Sinica

基　　金：国家自然科学基金(Nos.11774288,12074311);陕西省自然科学基金(No.2019-JC25)。

摘　　要：利用液相剥离法制备了WS_(2)纳米片,结合真空抽滤技术,控制上清液体积制备了不同厚度的WS_(2)薄膜。在此基础上,使用800 nm飞秒激光的Z扫描技术表征了WS_(2)纳米薄膜的三阶非线性吸收特性。研究发现,制备的不同厚度的WS_(2)都表现出可饱和吸收特性,可饱和吸收主要是由于单光子吸收所引起的泡利阻塞效应引起;随着厚度的增加,饱和强度基本不变,调制深度会有所提高,但是三阶非线性极化率虚部的绝对值和品质因子会降低。这主要是因为较厚的薄膜缺陷更多,更容易捕获光生载流子,从而三阶非线性吸收和厚度有一定的依赖关系。可饱和吸收可以用于调Q激光器以及锁模激光器,为WS_(2)薄膜在超快开关和超快激光的应用提供实验支持。Two-dimensional(2D)layered materials with excellent properties such as strong spin-valley coupling,high current on/off ratio and carrier mobility,have gained great attentions in optoelectronic applications including photodetectors,field effect transistors and light-emitting diodes.Meanwhile,many Novel Nonlinear Optical(NLO)phenomena such as saturable absorption,reverse saturable absorption and two-photon absorption have also been observed.Based on these nonlinear absorption behaviors,ultrafast photonic applications including Q-switching,mode locking and optical limiting have successfully been designed in 2D materials.The device performance is strongly dependent on their thicknesses due to tunable electronic properties with layer.For example,giant two-photon absorption can be observed in monolayer WS_(2) film with 1.9 eV while excellent saturable absorption has been demonstrated in multilayer.However,the related research about NLO nonparametric processes with layer thickness,which is crucial to design high performance photonic devices,was seldom reported due to uncontrollable thickness in large-area.Therefore,seeking for an efficient way to produce large-scale and controllable film is highly desirable.To date,mechanical exfoliation have been developed to acquire few-layer nanosheet through exfoliating bulk material layer by layer.However,these methods are low reproducibility and low yield and even limit their application in photonic devices.Compared with mechanical exfoliation method,liquid phase exfoliation was quickly developed and most 2D materials were successfully exfoliated to few-layer or monolayer nanosheet.The nanosheet dispersion can be used to form wafer-scale film by vacuum filtration technique,which provides an effective way to prepare large-area film.Herein,WS_(2) nanosheet dispersion was prepared by liquid phase exfoliation and then WS_(2) films with different thicknesses were prepared by a vacuum filtration method with different volumes.The atomic force microscopy confirmed the nanosheet length is

关 键 词：二硫化钨 三阶非线性 可饱和吸收 厚度依赖 Z扫描 

分 类 号：O437[机械工程—光学工程]