Abstract
In this paper, we analyze dynamics and frequency response of GaAs-based
microring modulators at the 1.55 $\mu$m using the finite-difference time-domain method. Two types of modulation
are investigated: pump-probe configuration and modulation of the coupling
coefficient. The pump-probe signals are tuned at separate resonance wavelengths
of the microring. Change of effective refractive index of the microring by
two-photon absorption is used to modulate the probe beam. By applying probe
beam in four timing configurations, it is shown that the wavelength shift
of the probe depends not only on the pump intensity but also on the interaction
length over which the pump and probe pulses overlap. It is also shown that
free-carrier absorption increases when the temporal width of pump signal is
wide enough. Modulation bandwidth of microring in the presence of nonlinear
effects is investigated and it is shown that the bandwidth is in 10 GHz range.
In order to increase the bandwidth of the intensity modulator, controlled
coupling is used. It is shown that in this case, modulation bandwidth of waveguide-ring
coupling strength becomes three times wider.
© 2012 IEEE
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