title: Optical Anisotropy of Black Phosphorus in the Visible Regime.
abstract: The striking in-plane anisotropy remains one of the most intriguing properties for the newly rediscovered black phosphorus (BP) 2D crystals. However, because of its rather low-energy band gap, the optical anisotropy of few-layer BP has been primarily investigated in the near-infrared (NIR) regime. Moreover, the essential physics that determine the intrinsic anisotropic optical property of few-layer BP, which is of great importance for practical applications in optical and optoelectronic devices, are 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. On the basis of the Fresnel equation, the intrinsic anisotropic complex refractive indices (n-iκ) in the visible regime (480-650 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 atom-thick light modulators, including linear polarizer, phase plate, and optical compensator in a broad spectral range extending to the visible window.
authors.forename: Nannan
authors.initials: N
authors.lastname: Mao
authors.forename: Jingyi
authors.initials: J
authors.lastname: Tang
authors.affiliation: Key Laboratory of Standardization and Measurement for Nanotechnology of Chinese Academy of Sciences, National Center for Nanoscience and Technology , Beijing 100190, PR China.
authors.forename: Liming
authors.initials: L
authors.lastname: Xie
authors.forename: Juanxia
authors.initials: J
authors.lastname: Wu
authors.forename: Bowen
authors.initials: B
authors.lastname: Han
authors.forename: Jingjing
authors.initials: J
authors.lastname: Lin
authors.forename: Shibin
authors.initials: S
authors.lastname: Deng
authors.affiliation: Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China , Beijing 100872, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.affiliation: School of Materials Science and Engineering, Shaanxi Normal University , Xi'an, 710062, PR China.
authors.forename: Hua
authors.initials: H
authors.lastname: Xu
authors.forename: Kaihui
authors.initials: K
authors.lastname: Liu
authors.forename: Lianming
authors.initials: L
authors.lastname: Tong
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang