We demonstrate the hallmark concept of periodic collapse and revival coherence in a room-temperature ensemble quantum dots (QDs) form 1.5-mm-long optical amplifier. Femtosecond excitation pulses induce coherent interactions with number discrete homogeneous QD subgroups within an inhomogeneously broadened ensemble, which interfere constructively to (CR). The amplitude decay CR is dictated by lin...

Quantum wire lasers are expected to require very low threshold currents owing to the nature of the 1 D density of states which develops a sharp peak at the band edge and ensures superior laser characteristics. However, carrier relaxation processes in quasi-lD structures may be much slower than in bulk material owing to reduction in the momentum space. For very long relaxation times, these equil...

We measured the ultrafast gain recovery dynamics of the ground-state transition in an ensemble of electrically pumped InGaAs/GaAs quantum dots having a nonequilibrium carrier distribution prepared by an optical prepump pulse. We find that the gain recovery dynamics after optical depletion by the prepump is faster than without prepump, an effect most pronounced at low temperature 15 K but observ...

Spatially, spectrally, and temporally resolved cathodoluminescence ~CL! techniques have been employed to examine the optical properties and kinetics of carrier relaxation for metalorganic chemical vapor deposition grown InGaN/GaN single quantum wells ~QWs!. Cathodoluminescence wavelength imaging of the QW sample revealed local band gap variations, indicating the presence of local In composition...

Recent success in the fabrication of axial and radial core-shell heterostructures, composed of one or more layers with different properties, on semiconductor nanowires (NWs) has enabled greater control of NW-based device operation for various applications. (1-3) However, further progress toward significant performance enhancements in a given application is hindered by the limited knowledge of ...

Temperature-dependent dynamics of phonon-assisted relaxation of hot carriers, both electrons and holes, is studied in a PbSe nanocrystal using ab initio time-domain density-functional theory. The electronic structure is first calculated, showing that the hole states are denser than the electron states. Fourier transforms of the time-resolved energy levels show that the hot carriers couple to bo...

We have examined the kinetics of carrier relaxation in GaAs/AlGaAs quantum wells ~QWs!, quantum wires ~QWRs!, and quantum boxes ~QBs! with time-resolved cathodoluminescence ~CL!. In the cases of QWRs and QBs, the nanostructures were grown via a size-reducing growth approach on pre-patterned GaAs~001! substrates composed of stripes and mesas, respectively. The growth involved deposition of multi...

The ultimate limitations on carrier mobilities in metal dichalcogenides, and the dynamics associated with carrier relaxation, are unclear. We present measurements of the frequency-dependent conductivity of multilayer dichalcogenide MoS2 by optical-pump terahertz-probe spectroscopy. We find mobilities in this material approaching 4200 cm2 V−1 s−1 at low temperatures. The temperature dependence o...