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The optical gain dynamics in an InGaAs/AlInAs quantum cascade laser is studied by midinfrared pump-probe experiments and electro-optic sampling. We find an extremely fast gain recovery time of <1 ps.
Time and phase resolved spectroscopy of broadband mid infrared pulses transmitted through the active medium of a mid infrared quantum cascade laser reveal the full complex refractive index and its derivatives over a wide spectral range. Using electro-optic sampling, we can monitor the optical response even above threshold and study effects of gain depletion and decoherence.
The spin relaxation within the radiative doublet of the exciton ground state in InAs/GaAs quantum dots is studied via ultrafast spectral hole burning spectroscopy. A biexcitonic resonance emerges due to relaxation of the exciton spin.
The electron relaxation dynamics in self-assembled InAs/GaAs quantum dots is investigated by tuning femtosecond mid-infrared pulses into resonance with intraband transitions and measuring the absorption as a function of time-delay after an interband pump pulse
Photoconductive Terahertz emitters with integrated Bragg mirrors are presented which show increased THz emission efficiency due to cavity enhanced absorption. These emitters also allow intracavity THz generation in mode-locked Ti:sapphire lasers.
Summary form only given. Several mechanisms for coherent THz emission from both semiconductor bulk and heterostructure devices have been presented. Recently, Sekine et al. reported on the optically pumped emission of THz radiation from grating-coupled intersubband plasmons in a doped single quantum well. We present experiments which show that modulation doped parabolic quantum wells (PQWs) emit coherent...
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