Low-threshold quantum-cascade lasers at 3.5 THz (lambda=85 mu m)

Chirped-superlattice quantum-cascade lasers are reported that emit at lambda similar to 85 mum (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(-2) were observed in pulsed and continuous-wave operation, respectively. For the latter, output powers of a few hundred microwatts are estimated at low temperatures. (C) 2003 Optical Society of America.