This equipment grant will be used for construction of a colliding pulse modelocked (CPM) dye laser system, consisting of an oscillator and amplifier. This apparatus which can generate pulses shorter than 100 femtoseconds will enable the PIs to study the fundamental electronic processes that allow or limit subpicosecond operation, and to develop and test new concepts in ultrafast electronics. The momentum and energy relaxation time of hot carriers in semiconductors is a critical parameter in physics and for devices. The relaxation time is usually not very well known but it is thought to be between <100fs and 10ps. The various relaxation process in quantum wells and amorphous semiconductors will be directly measured under a variety of conditions (doping, injected carrier density, lattice temperature). These results will be combined with those of ongoing experimental and theoretical effort. The propagation of ultrashort electrical pulses will also be used in a study of transient transport, including velocity overshoot, in semiconductors. The electrical output of a quantum well optical detector will be studied with the help of femtosecond pulses.
