Widely tunable ultra-stable and SI-traceable quantum cascade lasers for frequency metrology and midinfrared precise spectroscopy: application to space, atmospheric and fundamental physics

Post: Master internship in Experimental Molecular Physics
Location: Laboratoire de Physique des Lasers (LPL), CNRS-Univ Sorbonne Paris Nord, Villetaneuse, France
Team: Metrology, Molecules and Fundamental Tests (MMFT)
Advisors: Dr Benoît Darquié (
Dr Mathieu Manceau (
Contract: Fixed Term, 4-6 months, starting in Spring 2022

Internship Description:
Ultra-high spectral resolution molecular spectroscopy is an interdisciplinary field with fascinating and far-reaching applications ranging from fundamental physics to astrophysics, earth sciences, remote sensing, metrology and quantum technologies. Among recent instrumental advances, the stabilization of quantum cascade lasers (QCLs) on commercial optical frequency combs with traceability to primary frequency standards, a method recently implemented in our team, is a breakthrough technology. It offers an unprecedented level of precision and resolution in the mid-infrared, an essential region known as the molecular fingerprint region, which hosts a considerable number of intense vibrational signatures of molecules of various interests. While the need for ultimate frequency control is obvious for fundamental applications such as testing fundamental symmetries or measuring fundamental constants and their possible variations, other fields such as atmospheric monitoring have surprisingly the same requirement.
Molecular remote sensing measurements are often limited by the quality of spectroscopic data, resulting from the limited resolution of traditional spectrometers. The limited accuracy obtained for parameters affecting the line profile, such as frequency shifts and widths, leads to systematic biases in the determination of atmospheric species abundances, which is a crucial information for environmental and human health issues.
The techniques developed at the Laboratoire de Physique des Lasers can be used to overcome this type of bottlenecks. For example, we have recently improved by 3 order of magnitude the accuracy on some methanol rovibrational line centres compared to previous measurements reported in the literature. We are now adding a Fabry-Perot cavity to our spectrometer to perform cavity enhanced spectroscopy which will allow us to target more complex molecules of atmospheric, astrophysics and fundamental interest, and to improve our current spectroscopic resolution. During the internship, the student will continue this work. She/ will:
– improve and characterise the spectroscopic properties of the apparatus;
– perform measurements on relatively complex molecular systems of interest for atmospheric sciences (CH3SCH3), astrophysics (C3H6O3), and for probing the violation of fundamental symmetries (chiral organo-metallic species).

The proposed technology is at the forefront of time-frequency metrology and bring increasingly complex polyatomic molecular systems within reach of precision measurement experiments and frequency metrology. Finally, this work has also strong applicative and industrial perspectives, for example in medical diagnosis, detection of pollutants, hazardous materials or quantum technologies.

ultra-high resolution vibrational spectroscopy, mid-infrared, frequency metrology, Doppler-free methods, precision measurements, optical frequency comb lasers, quantum cascade lasers, molecular physics, quantum physics, optics and lasers, vacuum techniques, electronics, programming and simulation Relevant publications from the team: Santagata et al, Optica 6, 411 (2019); Argence et al, Nature Photon. 9, 456 (2015), arXiv:1412.2207


The applicant should be doing its master studies in a relevant area of experimental physics or chemical physics: atomic, molecular and optical physics, spectroscopy, lasers, quantum optics. She/he will be expected to display the initiative and creativity, together with the appropriate skills and knowledge, required to meet the project goals. Interested applicants should email a CV, a brief description of research interests and the contact details of 2 referents to M. Manceau ( and/or B. Darquié (