  Inspired by moth eyes, nature's most powerful antireflex, we present a
sub-wavelength SiC micropyramid design, which operates in the Reststrahlen band
of SiC, namely the spectral band of strong phonon-photon coupling in the SiC
material. While within this band SiC repels EM waves, we observe here a broad
low-reflectivity window with unique attributes, with distinct characteristics
different from typical dielectric moth-eye-like structures. To be specific,
while the latter systems are entirely symmetric, the reflection response of our
SiC micropyramid system can be highly asymmetric. In particular, the SiC
micropyramid system can be near-reflectionless for light impinging from the tip
side of the micropyramids and exhibits more than 90% reflection for light
impinging from the base side of the micropyramids, over a broad wavelength
range in the SiC Reststrahlen band. This strongly asymmetric reflection
response emanates from the cascaded coupling of vortex-like cavity modes at
each of the SiC blocks comprising the micropyramids and translates into a
strongly uni-directional absorber response. We discuss how, by virtue of
Kirchhoff's law, this strongly uni-directional superabsorber behavior implies a
strongly uni-directional emission profile that is important for one-way
infrared sources and passive radiative-cooling systems.
