MIOMD-XI Speakers    
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1.  Dr. Stéphane Schilt, Université de Neuchâtel, SWITZERLAND
Late-Breaking Results: Frequency Noise of a 4.6 µm DFB Quantum Cascade Laser measured from 130 K to 300 K
Speaker Biography: Dr Stéphane Schilt obtained his master degree in physics from the Swiss Federal Institute of Technology in Lausanne (EPFL) and his PhD in technical sciences in 2002 from the same institution for his work in trace gas sensing by laser spectroscopy. After a 3-year post-doc where he worked on photoacoustic spectroscopy and stabilized lasers, he joined the company IR Microsystems in Lausanne to develop low-cost gas sensors based on NIR lasers. Since 2009, he has been senior scientist at Laboratoire Temps-Fréquence at the University of Neuchâtel, Switzerland, where his research interest is focused on optical frequency combs for time and frequency metrology and QCL frequency-stabilization. He has published more than 25 papers in peer-reviewed journal and has co-authored over 50 contributions in international conferences.

Summary: We present an experimental study of the evolution of the frequency noise in a 4.55-µm distributed feedback quantum cascade laser (QCL) measured over a wide temperature range of 128-303 K. The frequency noise power spectral density is measured using different carbon monoxide absorption lines used as a frequency-to-voltage converter. An abrupt transition is observed in the laser frequency noise near 200K: the frequency noise is almost unaltered at T > 200K, while it increases exponentially at lower temperature. The corresponding laser linewidth is larger by a factor ten at 128K (10 MHz) compared to the sub-MHz value achieved at room temperature. The origin of the frequency noise in the QCL is shown to result from internal electrical noise in the QCL structure. Indeed, measurements of the electrical noise of the laser (voltage noise across the laser) showed to follow the same trend with respect to temperature as the frequency noise and linewidth.
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