Missions

This postdoctoral position is part of an interdisciplinary research project involving two teams at the University of Lille with complementary expertise, from the PhLAM laboratory (Physics of Lasers, Atoms and Molecules) and the IEMN (Institute of Electronics, Microelectronics and Nanotechnology). The goal is to develop a new class of semiconductor saturable absorbers (SESAMs) for ultrashort pulse, high-repetition-rate fiber lasers.

The core objective of the project is to model, design, and test ultrafast semiconductor structures capable of functioning as saturable absorbers—a key element for passive mode-locking in pulsed lasers [1], [2]. These structures will then be integrated into fiber laser cavities to evaluate their dynamic performance.

The major innovation of the project lies in the development of electrically tunable saturable absorbers: by applying a high-frequency RF electric field (up to several tens of GHz), the absorption properties of the component can be dynamically modulated via the Franz–Keldysh effect [3]. This modulation would ultimately enable active locking of the laser repetition rate to an external RF reference, opening new avenues in optoelectronic synchronization technologies, particularly for applications in telecommunications, metrology, and the generation of ultrahigh spectral purity signals.

This approach, based on fast temporal modulation of the effective bandgap in semiconductors, builds upon prior work on using the Franz–Keldysh effect for the detection of ultrafast signals [4]. The current project aims to extend this technique to the domain of mode-locked fiber lasers.

References
[1] U. Keller, “Recent developments in compact ultrafast lasers,” Nature, vol. 424, no. 6950, pp. 831–838, 2003.
[2] M. E. Fermann and I. Hartl, “Ultrafast fibre lasers,” Nature Photonics, vol. 7, no. 11, pp. 868–874, 2013.
[3] Y. Yacoby, “High-Frequency Franz-Keldysh Effect,” Physical Review, vol. 169, no. 3, pp. 610–619, 1968.
[4] J. F. Lampin, L. Desplanque, and F. Mollot, “Detection of picosecond electrical pulses using the intrinsic Franz-Keldysh effect,” Applied Physics Letters, 2001.

Activities

The recruited postdoctoral researcher will serve as the liaison between the two research teams, and will be responsible for:

- Electro-optical modeling of the components,

-Characterization of the fabricated devices,

-Integration and testing of the components within fiber laser cavities.

Skills

Candidates must hold a PhD in Physics, Photonics, or Electronics, with strong knowledge and proven experience in experimental physics and instrumentation.

Work Context

The work will be carried out mainly within the THz Photonics group at the Institute of Electronics, Microelectronics and Nanotechnology (IEMN) [https://www.iemn.fr/], located near the University of Lille campus. The postdoctoral fellow will work under the supervision of Dr. Emilien Peytavit and Jean-François Lampin

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.