The instantaneous optical frequency of an external-cavity quantum cascade laser (QCL) is characterized by comparison to a near-infrared frequency comb. Fluctuations in the instantaneous optical frequency are analyzed to determine the frequency noise power spectral density for the external-cavity QCL both during fixed wavelength operation and swept wavelength operation. This same combination of external-cavity QCL and comb can be applied to rapid, precise broadband spectroscopy.
Citation: Optics Express
Pub Type: Journals
continuous wave, cw, fiber comb, frequency comb, laser characterization, metrology, mid-infrared, mid-IR, QCL, quantum cascade laser spectroscopy