TY  - JOUR
AU  - Liu, Dong
AU  - Yu, Haitong
AU  - Yang, Zhen
AU  - Duan, Yuanyuan
PY  - 2016
TI  - Ultrathin planar broadband absorber through effective medium design
JO  - Nano Research
SN  - 1998-0124
SP  - 2354
EP  - 2363
VL  - 9
IS  - 8
AB  - Ultrathin planar absorbers hold promise in solar energy systems because they can reduce the material, fabrication, and system cost. Here, we present a general strategy of effective medium design to realize ultrathin planar broadband absorbers. The absorber consists of two ultrathin absorbing dielectrics to design an effective absorbing medium, a transparent layer, and metallic substrate. Compared with previous studies, this strategy provides another dimension of freedom to enhance optical absorption; therefore, destructive interference can be realized over a broad spectrum. To demonstrate the power and simplicity of this strategy, we both experimentally and theoretically characterized an absorber with 5-nm-thick Ge, 10-nm-thick Ti, and 50-nm-thick SiO2 films coated on an Ag substrate fabricated using simple deposition methods. Absorptivity higher than 80% was achieved in 15-nm-thick (1/50 of the center wavelength) Ge and Ti films from 400 nm to near 1 μm. As an application example, we experimentally demonstrated that the absorber exhibited a normal solar absorptivity of 0.8 with a normal emittance of 0.1 at 500 ℃, thus demonstrating its potential in solar thermal systems. The effective medium design strategy is general and allows material versatility, suggesting possible applications in real-time optical manipulation using dynamic materials.
UR  - https://doi.org/10.1007/s12274-016-1122-x
DO  - 10.1007/s12274-016-1122-x