Master thesis position: Using strong coupling to detect gas traces in the THz

Context and objectives

Halogen species (ie CH3X; OX and HX; XX being Cl, I or Br) in gas phase are produced by numerous industries, oceans and several other bio systems. During the past decades, researchers demonstrated their major role in the atmosphere. They act on pollutants and particles through reactional cycles and are involved in the radiative forcing. They are major players of the Earth’s energy budget and global warming. Still, today no technics exist able to measure these species at realistic concentration in real time.

In this multidisciplinary internship, we propose to implement an innovative physical concept shown on figure 1: coupling of the molecular frequency comb of a halogen gas as to the optical frequency comb of Fabry-Perot cavity. This coupling will enhance the light matter interaction and consequently enable to detect extremely small concentration of gas. We will probe this system using terahertz time domain spectroscopy (TDS) and a dedicated algorithm developed in the team to the study of gas by TDS.

Figure 1 : Left, molecular frequency comb (MFC) of bromomethane given as an example (changing the halogen will not change much the spectrum; other radicals change he spectrum but keep the comb behavior). Right the cavity made by two facing metasurface mirrors building the optical frequency comb (OFC) and enabling the coupling between the OFC and the MFC

The goal of this research internship is to launch this study together with a post doctoral fellow who will begin in January. The student will have to take over several of the many aspects gradually. The student will have to pick two tasks on which he/she will spend most of his/her time. This includes µ-nano fabrication, THz-TDS gas experiments and modeling of the strong coupling.

The student will work with a team of experienced researchers in the THz-Photonics group at IEMN Laboratory ( The group has a long lasting experience in the conception and realization of THz optoelectronic devices, and is fully equipped to carry out this project. The Laboratory hosts a 1500m2 clean-room with state of the art growth and fabrication facilities. IEMN is located in Lille, the capital of French Flanders, a vibrant city close to the Belgian border at 50 min by train from Paris-CDG airport.

We are looking for physics or engineering master student or equivalent. Having one of the following skills would greatly increase the chance of success of any application: Experimental optics – Spectroscopy – Python coding -µ-nano fabrication
The exact tasks in which the student will be involved will be discussed together with him/her and the team and will depends on its capacities and taste as the needs of the team. We strongly advice any potential candidate to contact us by email or elsewhere to begin the discussion before any formal application.

Key words: TeraHertz, Time domain spectroscopy, rotational spectroscopy

Possibility to go on with a PhD?
Yes, we are looking for two PhD student in the group next year one of them will have to deal with a really close subject.

Envisaged fellowship?
We already applied for several nationwide and European grants but the safest funding way will be to get a university of Lille grant. We are highly supported by the university and the chance of succes are very high in this call for a good candidate.

Unité d’accueil :
Centre de Micro et Nano fabrication
Avenue Poincaré


Contact: Dr Sophie Eliet / Dr Romain Peretti