High fluence ultrafast dynamics of semiconductor saturable absorber mirrors

The ultrafast nonlinear dynamics of InGaAs/InP semiconductor saturable abso rber mirrors are investigated using reflective pump-probe measurements. At high fluence, ultrafast induced absorption begins to dominate over absorpti on bleaching. Above the InGaAs quantum well band gap, the differential refl ectivity shows a similar to 1 ps transient due to nonequilibrium carrier dy namics. Below band gap, the signal is dominated by a strong two-photon abso rption component followed by induced absorption that decays with a time con stant of similar to 5 ps; these components are attributed to nonlinear abso rption and subsequent carrier diffusion in the InP layer. (C) 1999 American Institute of Physics. [S0003-6951(99)02950-2].