  Spin-sensitive saturation of absorption of infrared radiation has been
investigated in p-type GaAs QWs. It is shown that the absorption saturation of
circularly polarized radiation is mostly controlled by the spin relaxation time
of the holes. The saturation behavior has been investigated for different QW
widths and in dependence on the temperature with the result that the saturation
intensity substantially decreases with narrowing of QWs. Spin relaxation times
were experimentally obtained by making use of calculated (linear) absorption
coefficients for inter-subband transitions.
