  A non-autonomous dynamical system is proposed to study the synchronization in
networks of mutually coupled optically modulated hyperchaotic CO$_2$ lasers. By
the method of master stability function (MSF) it is shown that the stable
synchronous state can be reached for both the ring of diffusively coupled (RDC)
and star-coupled (SC) networks of at most $24$ nodes or oscillators. A
numerical simulation of the coupled $24$ hyperchaotic CO$_2$ lasers is also
performed to show that the corresponding synchronization error
$\lesssim10^{-6}$. Furthermore, the chimera states of the networks are found to
coexist in some intervals of time and the coupling strengths where the networks
are not synchronized, implying that the synchronization occurs only in some
specific ranges of values of the coupling strengths.
