Ultrafast saturable absorption at 1.55 mu m in heavy-ion-irradiated quantum-well vertical cavity

Measurements of absorption saturation in heavy-ion-irradiated InGaAs/InAlAs multiplequantum-well reflection-mode vertical-cavity devices have been per formed with short pulses at 1.55 mu m and repetition rates up to 10 GHz. Th e relaxation time was essentially independent of the pulse repetition rate and optical excitation fluence, with a lower value of 2.4 ps for an ion dos e of 10(12) cm(-2). Efficient optical switching was obtained, with a satura tion energy smaller than 12 pJ, a contrast ratio up to 3.5:1, and a switchi ng amplitude up to 20% of the incident signal. A relaxation model accountin g for capture and recombination on defect levels indicates an upper limit o f 2 ps of the defect level recombination time. (C) 2000 American Institute of Physics. [S0003-6951(00)03011-4].