  The vertical-cavity surface-emitting lasers (VCSELs) have emerged as a vital
approach for realizing energy efficient, high speed optical interconnects in
the data center and supercomputers. As of today, VCSEL is the most suitable for
mass production in terms of cost-effectiveness and reliability. However, there
are still key challenges for higher speed modulation above 40 GHz. Here, a
hexagonal transverse coupled cavity VCSEL adiabatically coupled through the
center cavity is proposed. A 3-dB roll-off modulation bandwidth of 45 GHz is
demonstrated, which is five times greater than a conventional VCSEL fabricated
on the same epi-wafer structure. While a parity time (PT) symmetry approaches
add loss to engineer the topological state of the laser system, here, a radical
paradigm shift with gain introduces symmetry breaking. This idea, then enables
a single mode operation with a side-mode suppression-ratio (SMSR) of > 30
decibels and signal-to-noise ratio (SNR) of > 45 decibels. The energy
distribution inside the coupled cavity system is also redistributed to provide
a coherent gain in a spatially separated system. Consequently, throughput power
is three times higher than that of the conventional VCSEL.
