ABSTRACT
Parametric phenomena in active media can be realised by a
time modulation of the medium parameters. If these parameters
change slowly in comparison with an electromagnetic field then
investigations can be made via adiabatic approximations that yield
a slow change of the results, without transients. These results
can be predicted relatively easily, but they are of little interest.
Transients become apparent in the other extremewhen themedium
parameters change rapidly with time. The main features of the
field transformation can be revealed by considering a simple law
for the variation of medium parameters with time that provides
a possibility to extract more information about the transformed
field behaviour, because exact solutions of the problem can be
constructed in this case. Another goal of the investigation of
transient electromagnetic phenomena is the problem of controlling
an electromagnetic signal by the temporal adjustment of medium
parameters, especially in a semiconductor material.
