Frequency metrology with quantum cascade lasers

We recently reported the first Doppler-limited absolute frequency measurement of CO2 transitions around 4.4 µm wavelength, by linking a DFB Quantum Cascade Laser (QCL) to an Optical Frequency Comb Synthesizer (OFCS). We further achieved sub-Doppler recording of these transitions, improving of about three orders of magnitude the measurement precision. We are exploring techniques able to significantly reduce the QCL jitter, in order to get metrological-grade QCLs for very demanding experiments in the frequency-domain. The latest experimental results in our group will be reported.