Faites connaître cette offre !
Reference : UMR7538-FREDUB-001
Workplace : VILLETANEUSE
Date of publication : Friday, September 27, 2019
Type of Contract : FTC Scientist
Contract Period : 8 months
Expected date of employment : 1 November 2019
Proportion of work : Full time
Remuneration : From 2695 € gross monthly according to experience
Desired level of education : 5-year university degree
Experience required : 1 to 4 years
The project 'Molecular thin cells' aims at fabricating thin cells, of thickness ranging from 5µm to 50nm filled with molecular gases. When the walls of a thin cell confine the molecular motion to distances smaller than the excitation wavelength, thin cell transmission spectroscopy is naturally sub-Doppler limited by the homogeneously broadened linewidth of molecular transitions. This phenomenon is usually referred to as Dicke narrowing. This opens the perspective of performing high-resolution molecular spectroscopy using very simple as well as compact experimental set-ups.
Our molecule of choice for this project is acetylene. Acetylene has a series of rovibrational transitions in telecommunication wavelength range (around 1.5µm) that give a frequency grid providing reliable references. Typically, the frequency of telecommunication lasers is stabilised on acetylene transitions using a non-linear saturated absorption set-up in a macroscopic acetylene-filled cell. Various cell designs, including fibered cells, have been commercialised finding various applications in communication and sensing industries.
Thin cell technology could be an excellent way to fabricate acetylene based frequency references that are miniaturised, compact and simple to use as they do not require complicated non-linear spectroscopic technics to obtain high-resolution signals. Here we propose to develop thin cell technology to achieve frequency references of similar accuracy and stability with the ones achieve in macroscopic set-ups. Additionally thin cells are also interesting for fundamental physics measurements. In particular, thin cells can be excellent platforms to perform spectroscopic measurements of the fundamental Casimir-Polder interaction between molecules and dielectric surfaces.
The post-doc researcher will fabricate thin cells in collaboration with the glass workshop and the Paris13 clean room. The cells have to be filled with molecular gas and then probed by infra-red rovibrational transmission spectroscopy using sensitive frequency modulation techniques to accentuate the narrow (high-resolution) molecular response. This work will be performed in the Laboratoire de Physique des Lasers (LPL) with the groups SAI (Atomic Spectroscopy at Interfaces) and MMTF (Metrology, Molecules and Fundamental Tests).
The post-doc researcher will have to learn the techniques already developed in our laboratory that will be necessary during the course of the 'Molecular thin cells' project. This includes thin cell fabrication techniques, as well as techniques required for frequency stabilization of semi-conductor lasers to perform high-resolution thin cell transmission spectroscopy. The post-doc researcher will then fabricate thin cells filled with molecules and probe them by monitoring the transmission of a ~1540nm laser. We will then explore the limits of thin technology in terms of spectral resolution and we will examine the possibility of using thin cells to perform molecule-surface interaction experiments.
The candidate should have a PhD in Physics and previous experience with of high-resolution atomic or molecular physics spectroscopy close to interfaces. Understanding of the quantum electrodynamics interaction between atoms or molecules and surfaces and understanding of spectroscopic effects of particle confinement will also be strongly appreciated. Finally, a previous experience with fabrication techniques will be a plus.
This activity takes place at the Laboratoire de Physique des Lasers (UMR 7538 CNRS-Université Paris 13), in Villetaneuse, within the SAI (Spectroscopie Atomiques aux Interfaces) and MMTF (Métrologie, Molécules et Tests Fondamentaux) groups. The project is supported by the Labex First-TF and the CNRS.
Constraints and risks
We talk about it on Twitter!