THz or FIR quantum-cascade lasers
For the THz or FIR spectral range, our investigations include
- ongoing activities on quantum-cascade lasers for the THz spectral range. These investigations are motivated by the search for intersubband emitters lasing at higher temperatures (>200 K) as well as for structures exhibiting broad gain spectra for tunable lasers.
- the optical coupling of two or three QCL cavities [1]. We have demonstrated the suppression of the longitudinal laser modes in two-sectioned QCLs due to interference effects of the laser light during its round trip. The mode behaviour depends on the driving currents partly affected by the level misalignment at high operating field strengths well as on the optical power of the laser modes due to saturation effects.
[1] M. Giehler, H. Kostial, R. Hey, and H. T. Grahn,
Suppression of longitudinal modes in two-sectioned, coupled-cavity GaAs/(Al,Ga)As terahertz quantum-cascade lasers,
Appl. Phys. Lett. 91, 161102, 3 pages (2007).

