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We have combined few-cycle THz spectroscopy with quantum cascade technology. This combination allows to perform unique THz time-domain measurements of THz-QCLs. By coupling the few-cycle THz pulse into the waveguide of the QCL, the processes within the active zone can be probed. This gives direct information regarding the energy, dynamics and coherence of transitions in the QCL structure. In addition,...
In this review, we report on the study of terahertz (THz) intersubband (ISB) transitions and on the optical devices based on them. We use time-resolved THz spectroscopy to examine ISB optical transitions in semiconductor quantum wells and quantum cascade lasers (QCLs). From these measurements, we obtain important information on the carrier relaxation, scattering mechanisms, and the gain. The waveguide...
Study of gain medium of terahertz quantum cascade lasers based on the interaction with broadband coherent radiation is presented. The phase resolved emitted field provides information on gain bandwidth, saturation recovery dynamics and coherent processes.
We present unique time-domain measurements of terahertz quantum cascade lasers. By coupling broadband terahertz pulses into the laser's waveguide the losses and gain in the frequency range 0.5 - 3.5 THz are determined. Furthermore internal processes and the laser dynamics can be tracked directly in the time- domain. The performance of THz-QCLs fabricated as double metal resonators is studied as a...
We present thermally activated absorption in a terahertz semiconductor heterostructure laser based on the bound-to-continuum design. By sensing broadband terahertz pulses transmitted through such laser structure the losses and the real device temperature are sensed.
Summary form only given. We have combined few-cycle THz spectroscopy with quantum cascade laser (QCL) technology. This combination allows to perform unique THz time-domain measurements of THz-QCLs. By coupling the few-cycle THz pulse into the waveguide of the QCL, the processes within the active zone can be probed. This gives direct information regarding the energy, dynamics and coherence of transitions...
We present fully developed model of the time-domain spectroscopy of the terahertz gain medium. Based on this model we simulated pulse amplification and the coherent response of the gain medium. We show that except of generally expected amplification of the pulse after interaction with the gain medium, other effects like the spectral shaping, spectral 'hole burning', and the phase coherence revival...
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