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Dr Pierre Bourdon

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Pierre Bourdon received the Ph.D. degree in physics and optics from the Ecole Polytechnique, Palaiseau, France, in 1995. From 1995 to 2004, he was a researcher at Départment Laser, Optique et Thermo optique, Centre Technique d'Arcueil, Délégation Générale pour l'Armement, Arcueil France. Since 2004, he is a researcher at Département Optique Théorique et Appliquée, Onera, the French Aerospace Lab, Palaiseau, France.
His main research interests are fiber lasers, nonlinear optics, optical parametric oscillators and solid-state lasers. He dedicates most of his work to the development of laser sources for military applications such as laser weapons and laser dazzling.


High power lasers for laser-matter interaction: an overview of available technologies
The directivity of laser light enables remote deposition of very high levels of power over small beam diameters resulting in extremely high power-density delivered on a target material.
This capability to emit very intense beams with lasers is commonly used in many industrial applications such as laser cutting, laser welding or laser marking. High power lasers can also be considered for military applications and integrated in anti-structure laser weapons aimed at destroying military targets such as ammunitions or vehicles from kilometers away. As an introduction, I will give a general presentation of these industrial and military applications and the thermal and thermo-mechanical effects they rely on.
The lecture will go into more details about the different laser technologies available today and their basic principles of operation. The pros and cons of the different families of lasers will be compared, especially in terms of emitted power and wall-plug efficiency but also in terms of practicality.
Most of the talk will be focused on the many advantages offered by solid state lasers as well as on their main limitation which is the build-up of thermal load in the laser material when high levels of average power are solicited. The specific case of the semiconductor lasers will be discussed and the reasons for their use as pump sources for other solid-state lasers rather than as high power beam generators will be given.
Among all the solid state lasers available, fiber lasers stand out as an interesting choice for industrial and military applications, and the levels of power and efficiency that can be achieved with this type of lasers will be detailed.
Finally, the challenge of integration of high power lasers on aircrafts or space vehicles with limited space, load and available power supply, will be addressed. Some ways to estimate the weight, volume and electrical consumption of a laser will be proposed and from these figures, the limitations in terms of emitted power for airborne or spaceborne laser systems will be inferred.

The challenge of asteroid and debris deflection with high power lasers: fiction or (future) reality?
After introducing, during the first lecture, the pros and cons of high power lasers for laser-matter interaction in the frame of industrial and military applications, this second talk will focus on the use of lasers for the specific challenge of asteroid and debris deflection.
This lecture will proceed through comparison with very similar applications: laser cutting and laser weapons. As a matter of fact, in both cases, the laser system has to deliver very intense beams on a remote target, an asteroid or debris in the first case, a material to be cut, a vehicle or an ammunition in the second case, in order to deliver energy on the remote target through heating of this target. In the case of laser cutting, matter melts under the high power laser beam resulting in drilling of the material. In the case of a laser weapon, the laser beam drills its access to the sensitive part of the target (either some explosive material, some fuel or some electronic component) through the superficial material of the target, thus resulting in its destruction.
Asteroid and debris deflection relies on similar effects: laser ablation of matter from the asteroid or the debris will induce a "rocket-like" effect and deflect the trajectory of the target.
In order to understand the main similarities and differences between laser cutting or laser weapon applications and space object deflection, the talk will discuss in more details the levels of power and characteristics of laser emission necessary to generate different physical effects from basic heating to more complex laser breakdown resulting in ablation of matter from the target.
Thresholds will be calculated and we will show how laser weapon ranges can be inferred from these threshold calculations in the case of laser weapon systems.
Referring to the limitations of high power lasers introduced during the first lecture, an analysis of the potential of high power lasers for this kind of purpose will be given and the main technological challenges yet to be overcome will be highlighted.
Finally, illustrating the talk by some examples of projects proposed recently, like the US DE-star project, feasibility of asteroid and debris deflection using lasers will be discussed and first technological milestones to be achieved in order to succeed will be proposed.

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