title: Broadband optical absorption by tunable Mie resonances in silicon nanocone arrays.
abstract: Nanostructure arrays such as nanowire, nanopillar, and nanocone arrays have been proposed to be promising antireflection structures for photovoltaic applications due to their great light trapping ability. In this paper, the optical properties of Si nanopillar and nanocone arrays in visible and infrared region were studied by both theoretical calculations and experiments. The results show that the Mie resonance can be continuously tuned across a wide range of wavelength by varying the diameter of the nanopillars. However, Si nanopillar array with uniform diameter exhibits only discrete resonance mode, thus can't achieve a high broadband absorption. On the other hand, the Mie resonance wavelength in a Si nanocone array can vary continuously as the diameters of the cross sections increase from the apex to the base. Therefore Si nanocone arrays can strongly interact with the incident light in the broadband spectrum and the absorbance by Si nanocone arrays is higher than 95% over the wavelength from 300 to 2000 nm. In addition to the Mie resonance, the broadband optical absorption of Si nanocone arrays is also affected by Wood-Rayleigh anomaly effect and metal impurities introduced in the fabrication process.
authors.affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Wang
authors.affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China.
authors.forename: R J
authors.initials: RJ
authors.lastname: Zhang
authors.affiliation: 1] Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China [2] Key Laboratory for Information Science of Electromagnetic Waves (MoE), Shanghai 200433, China [3] Ames Laboratory, U. S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: S Y
authors.initials: SY
authors.lastname: Wang
authors.affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China.
authors.forename: M
authors.initials: M
authors.lastname: Lu
authors.affiliation: National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China.
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China.
authors.forename: Y X
authors.initials: YX
authors.lastname: Zheng
authors.affiliation: Shanghai Engineering Research Center of Ultra-Precision Optical Manufacturing and Department of Optical Science and Engineering, Fudan University, Shanghai. 200433, China.
authors.forename: L Y
authors.initials: LY
authors.lastname: Chen
authors.affiliation: Ames Laboratory, U. S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Ye
authors.affiliation: Ames Laboratory, U. S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: C Z
authors.initials: CZ
authors.lastname: Wang
authors.affiliation: Ames Laboratory, U. S. Department of Energy and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Ho