Continuous, broad, and single-mode wavelength tuning of thermoelectrically cooled short-pulse quantum-cascade lasers is demonstrated with a combination of coarse grating tuning and fine phase tuning of the gain element. This approach overcomes the problem of a poor facet antireflection coating of the gain chip by shifting a Fabry-Perot longitudinal mode to coincide with the desired grating-selected wavelength. The 9-μm laser was tested with NH<sub>3</sub> gas absorption and showed fine frequency tuning at a rate of 31 MHz/step and a time-averaged linewidth of 500–750 MHz. The total tuning range was 9.08–9.36 μm and was limited only by the intrinsic gain of the device.
© 2003 Optical Society of America
Chuan Peng, Guipeng Luo, and Han Q. Le, "Broadband, Continuous, and Fine-Tune Properties of External-Cavity Thermoelectric-Stabilized Mid-infrared Quantum-Cascade Lasers," Appl. Opt. 42, 4877-4882 (2003)