Abstract
We report time-resolved measurements of the linewidth enhancement factors
($\alpha$-factors) $\alpha_{cr}$, $\alpha_{\rm CH}$, and $\alpha_{\rm TPA}$, associated with the adiabatic carrier
recovery, carrier heating, and two-photon absorption dynamical processes,
respectively, in semiconductor optical amplifiers (SOAs) with different degrees
of dimensionality–one InAs/InGaAsP/InP quantum dot (0-D), one InAs/InAlGaAs/InP
quantum dash (1-D), and a matching InGaAsP/InGaAsP/InP quantum well (2-D)—all
operating near 1.55-$\mu{\hbox{m}}$ wavelengths. We find the lowest $\alpha_{cr}$ values in the QD SOA, 2–10, compared
to 8–16 in the QW, and values of $\alpha_{\rm
CH}$ and $\alpha_{\rm TPA}$ that are also lower than in the QW. In the QD SOA, the $\alpha$-factors exhibit little
wavelength dependence over the gain bandwidth, promising for wide-bandwidth
all-optical applications. We also find significant differences in the $\alpha$-factors of lasers with
the same structure, due to the differences between gain changes that are induced
optically or through the electrical bias. For the lasers we find the QW structure
instead has the lower $\alpha$-factor,
having implications for directly modulated laser applications.
© 2008 IEEE
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