A novel design of double resonant plasmonic nanoantennas is proposed. Numerical simulations using finite-difference time-domain method show that the designed asymmetric H-shaped bowtie antenna can provide double resonances with a common electromagnetic hot spot in the antenna gap. These resonant modes are due to the plasmon hybridization in the asymmetric structure. In addition, a dual-narrow-band perfect absorber is achieved, consisting of the asymmetric structure positioned at a well-specified distance above a metal plane with a silica spacer layer. A broadband plasmonic absorber covering from 300 nm to 22 μm with over 95% absorption is also reported.
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