Quantum-well saturable absorber at 1.55 μm on GaAs substrate with a fast recombination rate

We propose and realize a structure designed for fast saturable absorber devices grown on GaAs substrate. The active region consists of a 1.55 mu m absorbing GaInNAsSb quantum well (QW) surrounded by two narrow QWs of GaAsN with a N concentration up to 13%. Photoexcited carriers in the GaInNAsSb QW are expected to recombine by tunneling into the wide distribution of subband gap states created in the GaAsN QW. An absorption study shows that edge energy and excitonic peak intensity of the GaInNAsSb QW are not affected by the proximity of the GaAsN QWs. Pump-probe measurements provide information on the carrier relaxation dynamics which is dependent on spacer thickness, as expected for a tunneling process. We show that this process can be enhanced by increasing the N content in the GaAsN layers. Using this design, we have realized a monolithic GaAs-based saturable absorber microcavity with a 1/e recovery time of 12 ps. (c) 2006 American Institute of Physics.