ULTRAFAST TRANSIENT GAIN IN TYPE-II MULTIPLE-QUANTUM WELLS

Gain for less than one picosecond is observed in a type II GaAs/AlAs m ultiple quantum well and compared to a type I multiple quantum well un der the same conditions. A sophisticated three-beam experiment is used to unambiguously determine the internal gain of the samples. This met hod is capable of measuring very small amounts of gain and applicable to a wide variety of situations. The observations are well explained b y a simple carrier scattering model. (C) 1996 American Institute of Ph ysics.