层间电荷转移增强二硫化铼/石墨烯异质结薄膜的反饱和吸收特性

Enhancement of Reverse Saturable Absorption of Rhenium Disulfide/Graphene Heterojunctions by Interlayer Charge Transfer

提高二维纳米材料的非线性光学响应,推动非线性光学在光电子领域的应用,是当前的一项巨大挑战,而构建高质量的范德瓦耳斯异质结,研究其非线性光学响应的内在机理,是解决途径之一。本文采用液相剥离结合真空抽滤技术,选择不同的混合方式(粉末混合、超声后混合、离心后混合),构建了三种二硫化铼/石墨烯异质结薄膜,并利用拉曼光谱仪、近红外吸收光谱仪以及原子力显微镜等对其进行了光学表征。采用自主搭建的高重复频率、窄脉宽飞秒Z扫描系统,重点研究了上述异质结薄膜在800 nm处的非线性光学特性,得到了其三阶非线性极化率虚部、品质因数等重要的非线性光学参数。结果表明:异质结的成功构建使得材料的非线性光学响应显著增强,超声后混合的二硫化铼/石墨烯薄膜的品质因数是纯二硫化铼薄膜的3.5倍,纯石墨烯的1.6倍;超声后混合的二硫化铼/石墨烯薄膜具有最高的反饱和吸收特性,其品质因数相较于粉末混合、离心后混合的异质结薄膜分别提高了44%和27%。本文为范德瓦耳斯异质结的制备提供了新思路,同时也为飞秒光限幅器件的研究打下了理论基础。

Improving the nonlinear optical(NLO) response of two-dimensional nanomaterials and motivating the NLO applications in optoelectronics are still highly challenging at present. One of the solutions is to construct van der Waals heterojunctions with high quality and clarify the internal mechanism in NLO response. In this study, rhenium disulfide(ReS;)/graphene heterojunction films are successfully fabricated by liquid exfoliation combining vacuum filtration, with different mixing approaches adopted, including powder mixing, mixing after ultrasonic treatment, and mixing after centrifugation. A Raman spectrometer, a near-infrared spectrometer, and an atomic force microscope are utilized to characterize the optical properties of the heterojunctions. The NLO properties of these films are investigated by a self-developed open-aperture Z-scan system with a high repetition frequency and a narrow pulse width which is equipped with an 800 nm femtosecond laser. The imaginary part of the third-order nonlinear polarizability and figure of merit(FOM) of these films are obtained. The results show that the NLO response of ReS;/graphene films is significantly enhanced owing to the successful heterojunction construction. The FOM of ReS;/graphene films prepared by mixing after ultrasonic treatment is 3.5 times that of ReS;film and 1.6 times that of graphene. The ReS;/graphene films in the case of mixing after ultrasonic treatment show the strongest reverse saturable absorption characteristics, and their FOM is 44% and 27% higher than that of films prepared by powder mixing and mixing after centrifugation, respectively. This paper provides a new idea for the fabrication of van der Waals heterojunctions and lays a theoretical foundation for the research of femtosecond optical limiters.