  We report on time-resolved optical and terahertz ultrafast spectroscopy of
charge-carrier dynamics in the room-temperature antiferromagnetic semiconductor
$\alpha $-MnTe. By optically pumping the system with 1.55 eV photons at room
temperature, we excite charge carriers in the conduction band through the
indirect band gap and investigate the dynamical response of nonequilibrium
states using optical as well as terahertz transmission probes. Three relaxation
processes are revealed by their characteristic relaxation times of the order of
1, 10, and 100~ps, whose exact values are functions of the pump fluence. For
high pump fluences nonlinear dependence on the pump fluence is observed both in
the optical and terahertz probes.
