  Several dynamical properties such as energy, momentum, angular momentum, and
optical helicity have been recently reexamined in dispersive and lossless
media. Here, we address a parallel derivation for the optical chirality,
extending it so as to include dissipative effects as well. To this end, we
first elaborate on the most complete form of the conservation law for the
optical chirality, without any restrictions on the nature of the medium. As a
result we find a general expression for the optical chirality density both in
lossless and lossy dispersive media. Our definition is perfectly consistent
with that originally introduced for electromagnetic fields in free space, and
is applicable to any material system, including dielectrics, plasmonic
nanostructures, and left-handed metamaterials.
