Femtosecond intersubband relaxation and population inversion in stepped quantum well

Intersubband relaxation dynamics in semiconductor quantum structures

We monitor the temporal evolution of the electron population in the first and second subband of an undoped GaAs/AlGaAs asymmetric double quantum well after interband optical excitation by using an interband pump/intersubband probe technique. The spacing between the two subbands is smaller than the longitudinal optical phonon energy. We extract an intersubband lifetime of T21 = 100 ps and a reco...

Continuous voltage tunability of intersubband relaxation times in coupled SiGe quantum well structures using ultrafast spectroscopy.

We demonstrate continuous voltage control of the nonradiative transition lifetime in semiconductor heterostructures. The results were obtained by picosecond time-resolved experiments on biased SiGe valence band quantum well structures using a free electron laser. By varying the applied voltage, the intersubband hole relaxation times for quantum well structures were varied by a factor of 2 as th...

Intrasubband and Intersubband Electron Relaxation in Semiconductor Quantum Wire Structures

We calculate the intersubband and intrasubband many-body inelastic Coulomb scattering rates due to electron-electron interaction in two-subband semiconductor quantum wire structures. We analyze our relaxation rates in terms of contributions from interand intrasubband charge-density excitations separately. We show that the intersubband (intrasubband) charge-density excitations are primarily resp...

Population inversion in an optically-pumped single quantum well

An optically-pumped intersubband laser generator is proposed in which the continuum states above an A1 0.2Ga 0.8.4s GaAs A1 o2Ga o.sAs single quantum well with a width of L = 17 nm serve as the highest level in a four-level laser system. The design allows much greater flexibility in the choice of pumping source and simplifies considerabb the device fabrication. We have obtained the electronic s...

Population inversion in optically pumped asymmetric quantum well terahertz lasers