Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques. With this active feedback, an 8.5-µm QC distributed-feedback laser is locked to the side of a rovibrational resonance of nitrous oxide (N<sub>2</sub> O) at 1176.61cm <sup>-1</sup> . A stabilized frequency-noise spectral density of 42Hz/√Hz has been measured at 100 kHz; the calculated laser linewidth is 12 kHz.
© 1999 Optical Society of America
(000.2170) General : Equipment and techniques
(120.4820) Instrumentation, measurement, and metrology : Optical systems
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(140.5960) Lasers and laser optics : Semiconductor lasers
Richard M. Williams, James F. Kelly, John S. Hartman, Steven W. Sharpe, Matthew S. Taubman, John L. Hall, Federico Capasso, Claire Gmachl, Deborah L. Sivco, James N. Baillargeon, and Alfred Y. Cho, "Kilohertz linewidth from frequency-stabilized mid-infrared quantum cascade lasers," Opt. Lett. 24, 1844-1846 (1999)