In a recent work, Horsley and coworkers (
\nNat. Photon.
\n,
\n9
\n(2015) 436) showed rather
\ninterestingly that planar dielectric media, for which the real and imaginary parts of the dielectric
\npermittivity are related by spatial Kramers-Kro
\nnig (KK) relations, are one-way reflectionless,
\nwhatever the angle of incidence. Such a fascinating property, besides extending our comprehension
\nof the fundamental phenomenon of reflection, may offer new ways for the design of ant…