Figure 1
Typical lasing spectra measured in pulsed mode at 10 K for three homogeneous QCLs, of different AR designs, targeted at frequencies of 2.5, 3.0 and 3.5 THz.

Figure 2
(a) Ppeak, and (b) Jth and Jmax, of 3THz QCLs as a function of nd at 10 K. Inset (a): Typical LIV characteristics of an as-cleaved 3THz QCL as a function of the heat sink temperature. Inset (b): Typical emission spectra of the device as a function of injection current density.

Figure 3
Typical CW LIV characteristics at 15 K of a 60 mm x 2.9mm DM waveguide heterogeneous THz QCL with 2mm absorbers on both sides of the device ridge. Inset: emission spectrum of the device at 2.1 x Jth.