An exciting completion of papers [16] and [17], centered around the
new closed-form representations (15) and (19) of the transmission
and reflection amplitudes in terms of modified Bessel functions.
These describe, in principle, the non-unitary quantum scattering in
complex potential $\exp ix$ and/or in its perturbations, but the
emphasis is fully transferred here to the experimentally productive
use of the underlying concept of the loss-gain symmetry in classical
optics. While working with a complex refractive index and studying,
typically, the unidirectional invisibility phenomena it is shown
that the related right-incidence enhancement arises through an
increase in the pulse length in the wave-packet scenario. Further
highlights of the text involve the rigorous confirmation that
although the invisibility itself is not quite exact, the modified
form of the unitarity (cf. ref. [18]) is strict and exact, indeed.


MR2904760 Jones, H. F. Analytic results for a $PT$-symmetric optical
structure. J. Phys. A 45 (2012), no. 13, 135306, 10 pp. 81Vxx
(81Qxx)