Développement d'une source laser à fibre dopée thulium pour la génération d'impulsions cohérentes, linéairement polairsée et de forte puissance à 2050nm

摘要

Fiber laser sources are useful in lots of domains, from telecommunication to medical and aerospace applications as they enable to achieve a good spatial coherence. They are compact and robust. Thulium doped fiber sources operating in the atmospheric transparency window and eye safe wavelength range of 1.9-2.1 µm are still being under developpement whereas they are highly desirable for many applications such as LIDAR or spectroscopy. Spectroscopy in the 6-12 µm band need specific pulsed coherent linearly polarized high-power single-frequency laser sources for pumping of optical parametric oscillator crystal as ZGP. But these characteristics increase the power limiting by a nonlinear effect, the stimulated Brillouin scattering (SBS). To fulfill this need, at first we studied thulium doped fibers and their pumping techniques to optimize the laser source architecture. In this way, we developed a numerical model for thulium-doped fiber amplifier able to estimate SBS power threshold. These studies allowed us to develop a master oscillator power amplifier limited by SBS to 530 W peak power. Then we use a SBS mitigation technique to increase the peak power to 1 kW without modification of the single-frequency linearly polarized high beam quality coherent parameters of the laser source (M²=1,2).