Continuous wave operation of quantum cascade lasers based on vertical transitions at lambda=4.6 mu m

Continuous wave operation of a quantum cascade laser at lambda=4.6 mu m is reported above liquid nitrogen temperature. Optical powers of 15 mW at 50 K and 2 mW at 85 K are reported. The single mode spectrum is temperature tunable over 1.8 cm(-1). A linewidth of 115 Mhz is measured with a Fabry-Perot on those free running devices. Gain measurements show evidence for ultra low linewidth enhancement factor alpha<0.1. These devices also operated in pulse mode with 20 mW peak power at 200 K. (C) 1996 Academic Press Limited