Narrow-line phase-locked quantum cascade laser in the 9.2 μm range

We report the operation of a 50 mW continuous-wave quantum cascade laser (QCL) in the 9.2 mu m range, phase locked to a single-mode CO2 laser with a tunable frequency offset. The wide free-running emission spectrum of the QCL (3-5 MHz) is strongly narrowed down to the kilohertz range, making it suitable for high-resolution molecular spectroscopy. (c) 2007 Optical Society of America.