  It is demonstrated that a new kind of low-loss surface electromagnetic wave
may propagate along a planar surface inside a lossy medium if the medium
permittivity changes continuously across such surface. Similar to surface
plasmons, the wavelength of this wave may be considerably shorter than the
light wavelength in free space, which may enable its applications in
super-resolution microscopy and nanolithography techniques. However, unlike
plasmonics-based nanophotonic devices, which are typically built using a very
limited number of low loss optical materials, the newly found class of surface
waves may be supported by a much broader range of lossy media. Such materials
as graphite seems to be ideal in UV nanophotonics applications. On the opposite
side of the electromagnetic spectrum, similar long-range surface
electromagnetic radio waves are capable of propagating underwater along a sandy
seabed, which may enable efficient underwater radio communication and imaging.
