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Reference : UMR7538-ANNAMY-001
Workplace : VILLETANEUSE
Date of publication : Monday, February 04, 2019
Type of Contract : FTC Scientist
Contract Period : 4 months
Expected date of employment : 1 April 2019
Proportion of work : Full time
Remuneration : From 2600 € brut mensuel (if just after PhD defense)
Desired level of education : PhD
Experience required : Indifferent
The project "Compact Frequency Comb" was initiated in 2014 within the Metrology, Molecules and Fundamental Tests team of Laboratoire de Physique des Lasers (UMR 7538 CNRS-Université Paris 13). Its aim is to explore the potential offered by semiconductor mode-locked lasers in the field of time-frequency metrology, in particular for the realization of fiber- devices, compact and transportable.
Those sources are 1.5 μm quantum-dot lasers initially developed by III-V lab for optical telecom. The strong coupling between modes by a four-wave mixing process within the material leads to passive mode locking and spontaneous generation of sub-picosecond pulses with repetition rates of a few tens of GHz. The optical modes of the laser are wide (typ 50 MHz), but the RF beat of all modes realized on a photodiode is very narrow (typ a few kHz).
Specific instrumentation for the characterization and stabilization of the comb has been developed. First optical injection experiments of a mode of a semiconductor mode-locked laser with a stable single-frequency source have shown the possibility of stabilizing of the whole comb: the injected mode acquires the spectral purity and stability of the single-frequency source and this improvement is transferred to the entire frequency comb, with slight degradation for remote modes.
The post-doc researcher will carry out a systematic study of the effect of injection on the semi-conductor frequency comb. The complete stabilization of the comb requiring to control the two degrees of freedom of the comb (frep and fceo), various approaches will be explored (dual-mode injection, single-mode injection associated with RF synchronization or optoelectronic feedback).
The head of the Metrology, Molecules and Fundamental Tests team is Benoît Darquié and the compact comb project is led by Frédéric Du-Burck (Professor) and Vincent Roncin (Associate professor).
The first task of the post-doc researcher will be to become familiar with the instrumentation developed in the team for the stabilization and characterization of mode-locked semiconductor lasers. He will then have to carry out a systematic study of the effect of the injection on the semi-conductor frequency comb in the following situations:
- Single mode injection;
- Dual-mode or tri-mode injection (by sideband generation);
- Single mode injection associated with RF synchronization;
- Single-mode injection associated with optoelectronic feedback.
In each case, he will evaluate the stability transferred to the different modes of the comb.
The candidate, PhD in Physics, must have experience in the use of fiber components at 1.5 μm as well as in the field of laser stabilization. An experience in optical injection is highly recommended.
This activity takes place at the Laboratoire de Physique des Lasers (UMR 7538 CNRS-Université Paris 13), in Villetaneuse, within the Metrology, Molecules and Fundamental Tests team. The work on compact frequency combs is conducted in partnership with III-V lab and FOTON (UMR 6082). It is supported by Labex First-TF (SPIRAL project) and CNRS.
Stability measurements require a reference at 1.5 μm. We benefit of a reference developed in the laboratory based on a transition of acetylene measured in cell in saturation spectroscopy and also of a reference from the SYRTE (CNRS-Observatoire de Paris) transmitted to the laboratory by optical fiber.
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