Novel mechanism for ultrafast optical nonlinearity in semiconductor laser amplifier using assist light

We have proposed and first demonstrated a novel mechanism for ultrafast optical nonlinearity in semiconductor laser amplifiers as saturable absorbers. We have obtained the reduced carrier lifetime of less than 70 ps by stimulated recombination due to a novel assist light. The further reduction of lifetime can be expected for shorter devices. This novel mechanism is promising for ultra-high repetition-rate gate function and noise reduction function, because there is little heat generation process through this fast stimulated emission.