Grating-tuned external-cavity quantum-cascade semiconductor lasers

Grating-coupled external-cavity quantum-cascade lasers were studied for temperatures from 80 to 230 K. At 80 K, a tuning range of similar to 65-88 nm are obtained for 4.5 and 5.1 mum laser amplifiers, respectively. The tuning ranges for both narrowed substantially with increasing temperature, to similar to 23 nm at 203 K. The threshold varied slowly versus wavelength, while the efficiency appeared to be close to optimum toward wavelengths shorter than the free running wavelength. (C) 2001 American Institute of Physics.