  Exchange interactions determine the correlations between microscopic spins in
magnetic materials. Probing the dynamics of these spin correlations on
ultrashort length and time scales is, however rather challenging, since it
requires simultaneously high spatial and high temporal resolution. Recent
experimental demonstrations of laser-driven two-magnon modes - zone-edge
excitations in antiferromagnets governed by exchange coupling - posed questions
about the microscopic nature of the observed spin dynamics, the mechanism
underlying its excitation, and their macroscopic manifestation enabling
detection. Here, on the basis of a simple microscopic model, we derive the
selection rules for cubic systems that describe the polarization of pump and
probe pulses required to excite and detect dynamics of nearest-neighbor spin
correlations, and can be employed to isolate such dynamics from other magnetic
excitations and magneto-optical effects. We show that laser-driven spin
correlations contribute to optical anisotropy of the antiferromagnet even in
the absence of spin-orbit coupling. In addition, we highlight the role of
subleading anisotropy in the spin system and demonstrate that the dynamics of
the antiferromagnetic order parameter occurs only in next-to-leading order,
determined by the smallness of the magnetic anisotropy as compared to the
isotropic exchange interactions in the system. We expect that our results will
stimulate and support further studies of magnetic correlations on the shortest
length and time scale.
