  Networks of optically coupled semiconductor lasers are of high interest for
fundamental investigations and for enabling numerous technological applications
in material processing, lighting and information processing. Still,
experimental realizations of large networks of such elements employing a
scalable concepts have so far been been lacking. Here, we present a network 22
of the vertical-cavity surface-emitting lasers in a $5 \times 5$ square lattice
array via. Crucially, the array allows individual control over each laser's
pump current, which we leverage spectrally align the array. Leveraging
diffractive coupling through an external cavity, 22 lasers are mutually
injection locked, and, furthermore, we demonstrate their simultaneous phase
locking to an external injection laser. The VCSEL network is a promising
platform for experimental investigations of complex systems and has direct
applications as a photonic neural network. The scalability of the concept opens
future possibilities for systems comprising many more individual lasers.
