A widely tunable 10-$\mu$m quantum cascade laser phase-locked to a   state-of-the-art mid-infrared reference for precision molecular spectroscopy
  We report the coherent phase-locking of a quantum cascade laser (QCL) at 10-$\mu$m to the secondary frequency standard of this spectral region, a CO2 laser stabilized on a saturated absorption line of OsO4. The stability and accuracy of the standard are transferred to the QCL resulting in a line width of the order of 10 Hz, and leading to our knowledge to the narrowest QCL to date. The locked QCL is then used to perform absorption spectroscopy spanning 6 GHz of NH3 and methyltrioxorhenium, two species of interest for applications in precision measurements. 
Papa Lat Tabara Sow (LPL), Sinda Mejri (LPL), Sean K. Tokunaga (LPL),   Olivier Lopez (LPL), Andrey Goncharov (LPL, ILP), B\...
physics.optics physics.atom-ph