  Spin-Vertical Cavity Surface Emitting Lasers (spin-VCSELs) are undergoing
increasing research effort for new paradigms in high-speed optical
communications and photon-enabled computing. To date research in spin-VCSELs
has mostly focused on Quantum-Well (QW) devices. However, novel Quantum-Dot
(QD) spin-VCSELs, offer enhanced parameter controls permitting the effective,
dynamical and ultrafast manipulation of their light emissions polarization. In
the present contribution we investigate in detail the operation of QD
spin-VCSELs subject to polarization modulation for their use as ultrafast light
sources in optical communication systems. We reveal that QD spin-VCSELs
outperform their QW counterparts in terms of modulation efficiency, yielding a
nearly two-fold improvement. We also analyse the impact of key device
parameters in QD spin-VCSELs (e.g. photon decay rate and intra-dot relaxation
rate) on the large signal modulation performance with regard to optical
modulation amplitude and eye-diagram opening penalty. We show that in addition
to exhibiting enhanced polarization modulation performance for data rates up to
250Gbps, QD spin-VCSELs enable operation in dual (ground and excited state)
emission thus allowing future exciting routes for multiplexing of information
in optical communication links.
