Adaptive optics systems offer the prospect of significantly increasing the capabilities of high-power laser focusability, which is currently limited by thermal distortions. Using novel wave-front measurement techniques that improve the stability of such systems and a downstream large-aperture deformable mirror that does not bear the usual limitations associated with precompensation, we have improved the focusability of a high-power (6×100-J, 1-ns) Nd:glass laser facility by a factor of 6. Measuring the wave front and the on-target focal spot at full power, we obtained after correction focal spots with a best Strehl ratio of 0.6. The pulse peak intensity could thus be increased to ∼2×10<sup>16</sup> W/cm<sup>2</sup>, a level beyond reach of the usual focal spot shaping techniques. We then used the near-diffraction-limited focal spots produced by this system to measure the laser–plasma coupling for a single, controlled filament of light and to underline the importance of the coupling among the numerous speckles within conventional multispeckled beams.
© 2003 Optical Society of America
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(140.3580) Lasers and laser optics : Lasers, solid-state
(140.6810) Lasers and laser optics : Thermal effects
(190.3100) Nonlinear optics : Instabilities and chaos
(350.4990) Other areas of optics : Particles
Benoit Wattellier, Julien Fuchs, Ji-Ping Zou, Jean-Christophe Chanteloup, Heidi Bandulet, Pierre Michel, Christine Labaune, Sylvie Depierreux, Alexis Kudryashov, and Alexander Aleksandrov, "Generation of a single hot spot by use of a deformable mirror and study of its propagation in an underdense plasma," J. Opt. Soc. Am. B 20, 1632-1642 (2003)