Excitonic light emission decay time measurements in moderately δ-doped GaAs/AlAs multiple quantum wells

The radiative recombination rate of moderately doped n-type and p-type GaAs/AlAs multiple quantum wells using a timecorrelated single photon counting system is presented. The experimental study has been obtained within a wide temperature range from liquid helium to room temperature and the work has focused on identifying photoluminescence decay rates based on freeexciton recombinations. It was found that the free exciton decay time was reduced in doped multiple GaAs/AlAs quantum wells, and that the reduction rate depends on both the concentration and doping type

High-Temperature Operation of Terahertz Quantum Cascade Laser Sources

Terahertz (THz) quantum cascade lasers (QCLs) are currently the most advanced electrically pumped semiconductor lasers in the spectral range 1-5 THz. However, their operation at room temperature is still an unresolved challenge. In this paper, we discuss our efforts to improve the temperature performance of these devices. In particular, we present THz QCLs that approach thermoelectric cooled operation and discuss factors that limit their high-temperature performance. We also discuss a different type of THz QCL source that produces coherent THz radiation without population inversion across the THz transition. These devices are based on intracavity difference-frequency generation in dual-wavelength mid-IR QCLs, and can now provide microwatt levels of coherent THz radiation up to room temperature. We discuss how the output power of these devices can be further improved to produce milliwatts of THz radiation at room temperature.Engineering and Applied Science