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Spectroscopy done on the light emitted by quantum cascade lasers (QCLs) provides only limited information on the optical , thermal, and temporal properties in such a laser. We study such lasers by time domain electric field spectroscopy of sub-picosecond pulse trains propagating through the QCL cavity. This is done by generating broadband mid-infrared pulses by phase matched difference frequency mixing...
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.
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...
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 spectral gain profile and modal gain coefficient can be measured by coupling a broadband mid infrared pulses generated by phase matched difference frequency mixing in a 30 mum thick GaSe crystal . This enables us to detect the transmitted light by coherent detection facilitating the electro optic effect in a crystal. The advantage of time resolved spectroscopy enables easy access to dynamic parameters...
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