We have investigated the optical absorption bleaching in several \(\hbox {GaAs}_{1-\mathrm{x}}\hbox {Bi}_{\mathrm{x}}\) layers of a different composition. Absorption saturation spectra in \(\hbox {GaAs}_{1-\mathrm{x}}\hbox {Bi}_{\mathrm{x}}\) samples have been measured by optical pump-and-probe technique, absorption bleaching was observed up to the wavelengths of 1,600 nm; its typical recovery times were of the order of several picoseconds. Short carrier lifetimes as well as saturation fluencies comparable to their values in the best known semiconductor saturated absorbers make the investigated layers promising for SESAM applications. We also demonstrated the experimental techniques suitable for carrier lifetime and semiconductor band gap determination by nonlinear absorption measurements.