Nanophotonics (Jan 2024)

Lithography-free directional control of thermal emission

  • Sarkar Mitradeep,
  • Giteau Maxime,
  • Enders Michael T.,
  • Papadakis Georgia T.

DOI
https://doi.org/10.1515/nanoph-2023-0595
Journal volume & issue
Vol. 13, no. 5
pp. 763 – 771

Abstract

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Blackbody radiation is incoherent and omnidirectional, whereas various novel applications in renewable energy require a degree of directional control of a thermally emitted beam. So far, such directional control has required nano-structuring the surface of a thermally emitting material, typically by forming diffraction gratings. This, however, necessitates lithography and usually results in polarization-dependent properties. Here, we derive analytical conditions for highly directional thermal emission using a planar 3-layer structure analogous to a Salisbury screen. We present design rules for maximizing the directionality of such structures. Notably, these design rules pertain to both linear polarizations, thus generalizing the principles of a grating for unpolarized light. We show that the key requirement to achieve such performance is ultra-high quality factor resonances in materials supporting phonon polaritonic modes, as those found in low-dimensional materials. We propose a realistic device based on hexagonal Boron Nitride and predict performances comparable to lithography-based nano-structures.

Keywords