Abstract
The development of novel thermal sources that control the emission spectrum and the angular emission pattern is of fundamental importance. In this paper, we investigate the thermal emission properties of semiconductor hyperbolic metamaterials (SHMs). Our structure does not require the use of any periodic corrugation to provide monochromatic and directional emission properties. We show that these properties arise because of epsilon-near-zero conditions in SHMs. The thermal emission is dominated by the epsilon-near-zero effect in the doped quantum wells composing the SHM. Furthermore, different properties are observed for s and p polarizations, following the characteristics of the strong anisotropy of hyperbolic metamaterials.
Highlights
The resonance frequency and directivity are driven by an ENZ effect and the optical anisotropy of the hyperbolic metamaterial
At given temperature T, wavelength λ, and direction θ, the thermal radiation intensity emitted from a body is
We find that a deeper understanding of the physical origin of the thermal radiation features, which are due to the occurrence of an epsilon-near-zero condition in the doped quantum wells, is only obtained through use of the superlattice model
Summary
The sample was grown using molecular beam epitaxy on a 0.65-mm-thick InP substrate with a 200 nm thick In0.52Al0.48As buffer layer. In contrast to the nearly flat and featureless mid-infrared thermal radiation spectrum observed in recent work on layered metal/dielectric hyperbolic metamaterials, we find strong directive and monochromatic emission features in proximity to the epsilon-near-zero frequency of the doped quantum wells of the SHM. We stress that this thermal emission behavior is obtained without the use of any periodic corrugation. Though all the thermal radiation characteristics are well recovered using an effective medium model for the SHM stack, their physical origin requires knowledge of the optical characteristics of the layers composing the SHM stack
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