  We study inelastic collisions of counter-propagating self-induced
transparency solitons in a homogeneously broadened two-level medium. The energy
of the pulse can be almost totally absorbed in the medium due to asymmetric
collision with a properly chosen control pulse. The medium state thus prepared
demonstrates the property of an all-optical diode which transmits pulses from
one direction and blocks from another. The saturation process of a controlled
absorption effect, local-field correction influence, and the parameter ranges
for the diode action are studied as well.
