| Abstract: | Dual-wavelength intersubband emission at 8 and 10 microm is reported in a three-level quantum-well system in which one electronic state is at the same time the lower level of the first optical transition and the upper level of the second. Results are presented for two different AlInAs/GaInAs quantum cascade structures featuring single-well active regions with two vertical transitions or double-well active regions with one diagonal and one vertical transition. Laser action has been achieved between the excited states of the single-well device and on the diagonal transition of the double-well structure. In the latter case the wavelength can be electric-field tuned by means of the Stark effect also above threshold. |
