  We propose a new mechanism to produce a meron-antimeron pair in a two
dimensional antiferromagnet with an ultrafast laser pulse via thermal Schwinger
mechanism. Unlike ultrafast skyrmion nucleation, this process conserves total
topological charge. We systematically show different stages of the dynamics and
define proper topological invariants to characterise the configurations. The
emergent structure can retain its topological structure for up to 100 ps. By
introducing a topological structure factor we show that pair formation is
robust against any random choice of initial magnetic configuration and can
survive against disorder. Our findings demonstrate that the rich world of spin
textures, which goes beyond conventional skyrmions, can be reached optically.
