Radiative thermal engineering with subwavelength metallic bodies is a key element for heat and energy management applications, communication and sensing.
The absorption and emission of infrared radiation by ultra-thin metallic films is a key element in several thermal engineering applications such as heat and energy management, and thermal camouflage. However, ultra-thin metallic films are broadband and low-efficiency emitters. Here, we demonstrate numerically and experimentally that metallic films placed on top of epsilon-near-zero (ENZ) substrates become narrowband and efficient thermal emitters. Our experiments show that ENZ-based emitters feature a narrow linewidth whose frequency positioning is robust against variations in the geometry of the system and the observation angle. Moreover, since ENZ emitters are based on the material properties of the substrate, no nanofabrication processes are needed, opening the pathway towards widefield and large-scale applications.
Epsilon-near-zero (ENZ) media have been very actively investigated due to their unconventional wave phenomena and strengthened nonlinear response. However, the technological impact of ENZ media will be determined by the quality of realistic ENZ materials, including material loss and surface roughness. Here, we provide a comprehensive experimental study of the impact of surface roughness on ENZ substrates. Using silicon carbide (SiC) substrates with artificially induced roughness, we analyze samples whose roughness ranges from a few to hundreds of nanometer size-scales. It is concluded that ENZ substrates with roughness in the few nanometer scale are negatively affected by coupling to longitudinal phonons and strong ENZ fields normal to the surface. On the other hand, when the roughness is in the hundreds of nanometer scale, the ENZ band is found to be more robust than dielectric and surface phonon polariton (SPhP) bands.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.