Ultra-Broadband Perfect Absorption with Stacked Asymmetric Hyperbolic Metamaterial Slabs.

We propose a method to realize ultra-broadband perfect absorption by using multiple slabs of asymmetric hyperbolic metamaterial (AHM) made of doped silicon nanowire arrays. Our numerical results show that the absorptance of the structure is greater than 0.99 in the wavelength range from <inline-graphic></inline-graphic> to <inline-graphic></inline-graphic> for an incident transverse magnetic (TM) plane wave at an angle of incidence equal to <inline-graphic></inline-graphic>. Moreover, the broadband absorptance can still be above 0.9 when the angle of incidence is in the range from <inline-graphic></inline-graphic> to <inline-graphic></inline-graphic>. The underlying mechanism is elucidated as due to the combination of matching of impedance at the interfaces and enhanced absorption in the AHM slabs of the structure. This work may provide in the design of metamaterial absorbers with some inspiring guidelines for obtaining highly enhanced absorption over an ultra-broadband and in a wide range of angle of incidence. [ABSTRACT FROM AUTHOR]