Titanium resonators based ultra-broadband perfect light absorber

We propose a new approach for achieving ultra-broadband perfect absorber by using titanium (Ti) resonators. Near-unity absorption with a high average absorptivity of 91.4% is achieved through the whole spectral range from 0.4 mu m to 2 mu m for the double-period lattice of Ti resonators array on the top of a silica layer coated on the opaque Ti substrate. In contrast to the common metal-insulator-metal (MIM) absorbers only with tens of nanometers absorption bandwidth, the Ti based ultra-broadband perfect absorber (T-UPA) can show a perfect absorption window (i.e., the absorptivity exceeding 90%) with the spectral bandwidth over 1007 nm from visible to near-infrared region (i.e., from 0.485 mu m to 1.492 mu m). The cooperative effects of the propagating surface plasmons and the corresponding localized plasmonic resonances of Ti resonators contribute to the broadband absorption response. Moreover, the ultra-broadband perfect absorption is polarization-independent and angle insensitive, which hold the proposed T-UPA with strong practicality and high tolerance in the complex electromagnetic environment (ie. sun radiation). Furthermore, the absorption window for this T-UPA can be greatly broadened via using a thin anti-reflection coating film, which shows a perfect absorption with the bandwidth of 1555 nm in the visible and near-infrared range. The numerically demonstrated thin-film absorber configuration facilitates the scalability to optoelectronics applications such as thermal photovoltaics and hot-electron devices.