Broadband directional control of thermal emission

Broadband thermal beaming Thermal radiation emits over a wide range of wavelengths and over a wide range of angles. Xu et al. constructed a material that allows a range of wavelengths to emit over a much narrower range of angles. This property allowed the authors to beam thermal energy preferentially in one direction. The strategy requires carefully exploiting stacks of epsilon-near-zero films in which the angular range of thermal emission is controlled by the film thickness. This design could be useful in thermal camouflage and passive radiative cooling applications. Science , this issue p. 393