Nannan Mao,1 Jingyi Tang,2 Liming Xie,3 Juanxia Wu,1 Bowen Han,1 Jingjing Lin,1 Shibin Deng,1 Wei Ji,4 Hua Xu,5 Kaihui Liu,2 Lianming Tong, 1* Jin Zhang1,*
1 Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural, Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
2 State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, School of Physics, Peking University, Beijing 100871, China
3 Key Laboratory of Standardization and Measurement for Nanotechnology of Chinese Academy of Sciences, National Center for Nanoscience and Technology, Beijing 100190, P. R. China
4 Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
5 School of Materials Science and Engineering, Shaanxi Normal University, Xi’an, 710062, P. R. China
DOI:10.1021/jacs.5b10685 Publication Date:
The striking in-plane anisotropy remains one of the most intriguing properties for the newly rediscovered black phosphorus (BP) two-dimensional (2D) crystals. However, due to its rather low energy band gap, the optical anisotropy of fewlayer BP has been primarily investigated in the near-infrared (NIR) regime. Moreover, the essential physics that determines the intrinsic anisotropic optical properties of few-layer BP, which is of great importance for practical applications in optical and optoelectronic devices, is still in the fancy of theory. Herein, we report the direct observation of the optical anisotropy of few-layer BP in the visible regime simply by using polarized optical microscopy. Based on the Fresnel equation, the intrinsic anisotropic complex refractive indices (n-iκ) in the visible regime (480 nm–650 nm) were experimentally obtained for the first time using the anisotropic optical contrast spectra. Our findings not only provide a convenient approach to measure the optical constants of 2D layered materials, but also suggest a possibility to design novel BP-based photonic devices, such as atomic-thick light modulator, including linear polarizer, phase plate and optical compensator in a broad spectral range extending to the visible window.