Context : With the contribution of atomic spectroscopy, MEMS technologies and integrated photonics, miniaturized atomic clocks, sensors and instruments have been developed for around 20 years [1]. This field of research, initiated in 2004 with
the demonstration at NIST of the first chip-scale atomic clock (CSAC), has since experienced growing popularity, due to its strategic interest and the plethora of applications (GNSS, secure communications, PNT systems, etc.) it covers. Current commercial CSACs lose about 1 microsecond per day, a hundred times less than quartz oscillators, within a comparable volume-consumption budget. However, the frequency noise of their laser (VCSEL) limits their short-term
frequency stability while the presence of a buffer gas pressure in their cell induces a collisional shift that compromise their long-term stability.[...] In this context, based on the experience acquired at FEMTO-ST, the PhD thesis targets the development, progress, and metrological characterization of an ultra-stable microcell optical reference based on two-photon transition of Rb atom at 778 nm. Improved fractional frequency stability in the 10-14 range at 1 s and 1 hour integration time is targeted in
a very simple laser system architecture. Such an optical reference might contribute to the positioning or navigation of GNSS-denied vehicles, nano-satellites, ships, and could find interest in the implementation of ambitious space missions
that require precise timekeeping.

Candidate Profile : 
The candidate should appreciate applied physics, for working in a highly-interdisciplinary subject that implies lasers, optics, quantum physics, CAD (physics package design), and electronics & instrumentation (Python preferred). The candidate
should be attracted by high-precision metrology. Some experience with clean-room techniques might be a plus-value.
Environment and application
The PhD candidate will work at the interface between the OHMS and MOSAIC groups at FEMTO-ST, Besançon, France. The candidate will interact with researchers, engineers, technicians and will benefit from the support and skills of
FEMTO-ST internal services (electronics/mechanics/computing), with access to a large park of instruments dedicated to time-frequency metrology and microfabrication platform (MIMENTO). The candidate will present his/her work in high-
impact scientific journals and international conferences.
PhD thesis funding: 50% CNES (French Space Agency), 50 % other source
Start date: October 2026
Application: https://recrutement.cnes.fr/fr/annonces (open from 02 Feb. to 13 March 2026).