ABSTRACT
This chapter focuses on some unique mid-infrared (IR) radiative properties enabled by doped-Si nanostructures and metamaterials for applications in plasmonic sensing, subwavelength thermal imaging, and thermal management. It discusses low-loss all-angle negative refraction in the mid-IR based on doped-Si nanowire arrays. At oblique incidence, the figure of merit (FOM) counterintuitively increases with the material loss in the direction along the optical axis of the metamaterials. The underlying physical mechanisms accounting for the large FOM are elaborated based on the loss-enhanced transmission, impedance matching, and absence of resonances. The chapter reviews the capability to achieve tunable omnidirectional perfect absorption of mid-IR electromagnetic waves via doped-Si metamaterials. It shows the utilization of doped-Si-based metamaterials or metasurfaces in enhancing near-field thermal radiation, which has promising applications in energy harvesting, heat dissipation, nanomanufacturing, as well as noncontact thermal diodes and transistors.
