Chirped-superlattice quantum-cascade lasers are reported that emit at λ~85 μm (3.5 THz), which is to the authors' knowledge the longest wavelength demonstrated so far with this technology. Collected peak output powers of 1.5 mW per facet were measured at liquid-helium temperature, and a maximum operating temperature of 45 K was reached. Record low-threshold-current densities of 95 and 115 A cm<sup>-2</sup> were observed in pulsed and continuous-wave operation, respectively. For the latter, output powers of a few hundred microwatts are estimated at low temperatures.
© 2003 Optical Society of America
Rüdeger Köhler, Alessandro Tredicucci, Fabio Beltram, Harvey E. Beere, Edmund H. Linfield, A. Giles Davies, and David A. Ritchie, "Low-threshold quantum-cascade lasers at 3.5 THz (λ = 85 μm)," Opt. Lett. 28, 810-812 (2003)