30 June 2017 – Thesis defense of Nicolas VON BANDEL

Nicolas VON BANDEL will defend his thesis on 30 June 2017 at 14:00, 0C-140 (Auditorium) – III-V Lab Campus Polytechnique 1 avenue Augustin Fresnel 91767 Palaiseau on the subject “Development and study of low noise laser diodes emitting at 894 nm for compact cesium atomic clocks”. This work was a collaboration between Institut d’Electronique et des Systèmes (Montpellier) and III-V Lab (Palaiseau).

Abstract : This PhD work deals with the design, the fabrication and the study of high-coherence semiconductor laser sources emitting at 894 nm, for application to compact, optically-pumped cesium atomic clocks in an industrial context. We are particularly interested in the electrically pumped ”Distributed-Feedback” in-plane laser diodes (DFB). The aim is to obtain a low-threshold, single-mode laser with high optical efficiency and a linewidth of less than 1 MHz. We first deal with the design and first-order characterization of the DFB diodes until they are put into modules for the clock. We then carry out an in-depth study of the physical properties of the laser emission in terms of coherence time. For that purpose, a new universal method for characterizing the optical frequency noise is introduced. Finally, we look further into the spectral properties of the emission in a servo configuration on a fluorescence line of the cesium (”Dither-Locking”). We show that the intrinsic properties of the component satisfy the requirements of the industrial system as defined in the study.

Keywords : Laser diodes, low noise, 894nm, cesium atomic clocks, frequency noise metrology, linewidth in servo