A unipolar intersub-band semiconductor laser operating above liquid nitrogen temperature at 4.3 µm wavelength is reported. The measured optical power in pulsed operation is 30 mW at 102 K and the slope efficiency 0.1 W/A. Strong line-narrowing above threshold and well resolved longitudinal modes are observed up to 125 K. This new light source, called the quantum cascade laser, is based on sequential photon emission in a staircase/coupled quantum well AlInAs/GaInAs structure grown by MBE and its wavelength can be tailored in an extremely wide region.
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Faist et al. (1994) studied this question.
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