a route to unusually broadband plasmonic absorption spanning from visible to mid-infrared

In this paper, a route to ultra-broadband absorption is suggested and demonstrated by a feasible design. the high absorption regime (absorption above 90%) for the suggested structure ranges from visible to mid-infrared (mir), i.e., for the wavelength varying from 478 to 3278 nm that yields an ultra-wide band with the width of 2800 nm. the structure consists of a top-layer-patterned metal-insulator-metal (mim) configuration, into the insulator layer of which, an ultra-thin 5 nm layer of manganese (mn) is embedded. the mim configuration represents a ti-al2o3-ti tri-layer. it is shown that, without the ultra-thin layer of mn, the absorption bandwidth is reduced to 274 nm. therefore, adding only a 5 nm layer of mn leads to a more than tenfold increase in the width of the absorption band. it is explained in detail that the physical mechanism yielding this ultra-broadband result is a combination of plasmonic and non-plasmonic resonance modes, along with the appropriate optical properties of mn. this structure has the relative bandwidth (rbw) of 149%, while only one step of lithography is required for its fabrication, so it is relatively simple. this makes it rather promising for practical applications.