2.9 THz quantum cascade lasers operating up to 70 K in continuous wave

We report the operation of a quantum cascade laser emitting at a 103 mum wavelength (2.9 THz). The active region is based on a bound-to-continuum design allowing a low parasitic leakage current, and a high upper-to-lower-state lifetime ratio. The latter is demonstrated by a pronounced decrease of the differential resistance at threshold, which is visible up to high temperatures, and by a weak temperature dependence of the slope efficiency. At 4 K, we report a threshold current density of only 105 A/cm(2) both in pulsed and continuous-wave operation, and an emitted peak power of 15 mW independent of the duty cycle. Maximum operating temperatures of 95 K and 70 K are observed in pulsed and continuous wave modes, respectively. (C) 2004 American Institute of Physics.