Abstract:
The temporal evolution of the α-factor during pumpprobe
experiments in semiconductor optical amplifiers (SOAs) is
not constant but varies strongly with time. It even takes on negative
values for short periods of time. As a consequence, cross-phase
modulation (XPM) effects usually lag behind cross-gain modulation
effects by several picoseconds. This delay has important
consequences for ultrafast operation of all-optical devices based
on SOAs. It actually means that not every scheme will be suited
for ultrafast operation. In order to properly model the XPM and
phase variations within an SOA during a pump-probe experiment,
a new parameterization for the α-factor is introduced. Inclusion
of this model leads to an excellent agreement with the recent
160-Gb/s experiments for both phase and amplitude evolutions of
the respective signals with time.
