• quantum-cascade laser;
  • terahertz;
  • selective injection scheme;
  • LO-phonon scattering


The terahertz quantum cascade laser (THz-QCL) is a promising compact THz laser source with high output power and narrow emission line width, and could be put to use in a variety of applications. However, the operating temperature of lower frequency (< 2 THz) QCLs is particularly low, and is limited by the kBT line. This paper demonstrates a 1.9 THz GaAs/Al0.175Ga0.825As QCL operating at temperatures much higher than the kBT line. A selective injection scheme (using a four-level design) with high-Al composition barrier was used to build the low-frequency QCL with high operating temperature. We succeeded in surpassing the kBT line limit for a 1.9 THz QCL that operates up to 160 K (∼1.8 ħw/kB). The selective injection 1.9 THz QCL shows one-frequency lasing operation over the entire injection bias voltage range. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)