  Transformation-based cylindrical cloaks and concentrators are illuminated
with non-monochromatic waves and unusual effects are observed with interesting
potential applications. The transient responses of the devices are studied
numerically with the Finite-Difference Time-Domain method and the results are
verified with analytical formulas. We compute the effective bandwidth of
several cloaking schemes as well as the effect of losses on the performance of
the structures. We also find that narrowband behavior, frequency shift effects,
time delays and spatial disturbances of the incoming waves are dominant due to
the inherently dispersive nature of the devices. These effects are important
and should be taken into account when designing metamaterial-based devices.
