QUANTUM CASCADE LASER - A NEW OPTICAL SOURCE IN THE MIDINFRARED

A unipolar intersubband semiconductor laser operating above liquid nitrogen temperature at 4.26 mu m wavelength is reported. The measured optical power in pulsed operation for a 1.2 m long device is 22 mW at 10 K and 9 mW at 90 K. Strong line-narrowing above threshold and well resolved longitudinal modes are observed. This new light source, called a quantum cascade laser, is based on sequential photon emission in a staircase/coupled quantum well AlInAs/GaInAs structure grown by molecular beam epitaxy. As the transitions arise between quantum confined states, its wavelength can be tailored in an extremely wide wavelength region while keeping the same heterostructure material.