Quantum cascade laser at Hz-level by use of a frequency comb and an optical link

We present a frequency chain which enables to transfer coherently the stability and the accuracy of an ultrastable laser emitting at 1.54 μm to the mid-infrared region. It includes an optical frequency comb and an ultrastable 1.54 μm frequency signal, referenced to primary standards and transferred from LNE-SYRTE to LPL through an optical link. This system gives us the ability to transfer frequency stability in the range of 10−15 and accuracy in the range of 10−14 from 1.54 μm to a wide spectral range in the mid-infrared domain. With this set-up, we stabilized a Quantum Cascade Laser emitting at 10.3 μm at an unprecedented Hz-level.