Enhanced absorption of metals over ultrabroad electromagnetic spectrum

Metals are usually highly reflective for electromagnetic waves, especially at far-infrared and terahertz frequencies. Using a femtosecond laser structuring technique, near-perfectly reflective metals are transformed to highly absorptive over an ultrabroad electromagnetic spectrum, ranging from ultraviolet to terahertz. Absorptance of the processed metal is directly measured in the terahertz region using a calorimetry technique, and the measurements show that absorptance of the processed metal is enhanced by more than thirty times over its intrinsic value.