Doctor Stéphane Coen

Contact details
Building 303, Room 615
Phone: +64 9 373 7599 ext 88841
Email: s.coen@auckland.ac.nz

I graduated Civil Engineer in Physics from the Université libre de Bruxelles (ULB) in 1996. I then worked towards the PhD degree at the Optics and Acoustics Department of the Applied Science Faculty of ULB thanks to a Doctoral fellowship of the Belgian Fund for Scientific Research (FNRS). I got the PhD degree in Applied Physical Sciences in December 1999 by defending a thesis entitled "Passive nonlinear optical fibre resonators: Fundamentals and applications" (This thesis is available in PDF format on demand). From May 2000 to October 2001, I was a visiting Post-doctoral Research Fellow at the Laser Laboratory of Prof. John D. Harvey in the Physics Department of The University of Auckland during which I started working on supercontinuum generation in photonic crystal fibres. During that period, I was still supported by the Belgian FNRS, from which I got a Chargé de recherches fellowship in October 2000. I came back to Brussels in November 2001 to complete my FNRS fellowship. In December 2003, I was appointed Lecturer at the Physics Department in Auckland University. I have been promoted to Senior Lecturer in February 2006. I am a Member of The Optical Society of America.

• Nonlinear optics
• Fibre optics
• Nonlinear passive resonators
• Supercontinuum generation
• Fibre lasers

I am involved with theoretical and experimental studies of fundamental nonlinear optical phenomena in optical fibres with the aim of investigating potential applications to telecommunications and other domains.

During my PhD in Brussels, I have focused on the study of the dynamics of passive nonlinear optical fibre resonators, investigating optical bistability, period-doubling instabilities and optical chaos, and several regimes of intracavity modulation instabilities. This has led to the demonstration of a continuous-wave ultrahigh repetition rate laser source based on modulation instability and operating at more than 100GHz. The structural simplicity of passive optical fibre cavities has also been used to investigate more fundamental nonlinear dynamics such as a competition between a dispersive and a convective transport mechanism. This latter aspect has been dramatically illustrated by the experimental demonstration of the inhibition of optical bistability in synchronously pumped nonlinear cavities in presence of a cavity synchronisation mismatch smaller than 1% of the pump pulse width.

While in Auckland, I have started working on supercontinuum generation, a process where a single frequency laser beam is converted into a white light continuum containing light spanning two octaves in frequency (ie, a laser rainbow extending from the ultra-violet well into the infra-red). Particular interest has been paid to the study of the various mechanisms underlying the spectral broadening through experiments and numerical simulations. I have also been investigating the coherence and noise properties of these light sources, both under pulsed and continuous-wave pumping conditions. This work has been the object of a review paper to be published in 2006 in Reviews of Modern Physics.

Supercontinuum generation in fibres being strongly connected to stimulated Raman scattering, I have paid a particular attention to this process. In particular, I have studied the intricate coupling between parametric and Raman interactions. I am currently interested in mode-locked Raman fibre lasers and in using Raman scattering to develop new techniques for the characterisation of fast intensity fluctuations that affect all types of lasers.

Download a full list of publications below.