Ultrafast gain recovery and modulation limitations in self-assembled quantum-dot devices

Measurements of ultrafast gain recovery in self-assembled InAs quantum-dot (QD) amplifiers are explained by a comprehensive numerical model. The on ex cited state carriers are found to act as a reservoir for the optically acti ve ground state carriers resulting in an ultrafast gain recovery as long as the excited state is well populated. However, when pulses are injected int o the device at high-repetition frequencies, the response of a on amplifier is found to be limited by the wetting-layer dynamics.