  The time evolution of magnetization induced by circularly polarized light in
a $S=1$ Heisenberg chain with large, easy--plane anisotropy is studied
numerically and analytically. Results at constant light frequency
$\Omega=\Omega_0$ are interpreted in terms of absorption lines of the
electronic spin resonance spectrum. Applying a time dependent light frequency
$\Omega=\Omega(t)$, so called chirping, is shown to be an efficient procedure
in order to obtain within a short time a large, controlled value of the
magnetization $M^z$. Furthermore, comparison with a $2$ - level model provides
a qualitative understanding of the induced magnetization process.
