High power CW (continuous wave) polycrystalline Nd:Y 3 Al 5 O 12 (Nd:YAG) ceramic rod laser was demonstrated for the first time. The maximum output power of 31 W with a 18.8% slope efficiency was obtained at 1064 nm using 214.5 W/808 nm laser diode pumping.

We describe a novel scheme consisting of two deformable bimorph mirrors that can free ultrashort laser pulses from simultaneously present strong wave-front distortions and intensity-profile modulations. This scheme is applied to the Max-Planck-Institut für Quantenoptik 10-TW Advanced Titanium-Sapphire Laser (ATLAS) facility. We demonstrate that with this scheme the focusability of the ATLAS pulses can be improved from 10(18) to 2x10(19) W/cm(2) without any penalty in recompression fidelity.

The bimorph deformable mirror with a diameter of 320 mm, including 127 control electrodes, has been developed and tested. The flatness of the initial mirror surface of about 1 μm (P-V) was achieved by mechanically adjusting the mirror substrate fixed in the metal mount. To correct for the aberrations and improve the beam focusing in the petawatt Ti:Sa laser, the wide-aperture adaptive optical system with the deformable mirror and Shack–Hartmann wavefront sensor was developed. Correction of the wavefront aberrations in the 4.2 PW Ti:Sa laser using the adaptive system provided increases the intensity in the focusing plane to a value of 1.1 × 1023 W/cm2

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 (6ϫ100-J, 1-ns) Nd:glass laser facility by a factor of 6. Measuring the wave front and the ontarget 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 ϳ2ϫ10 16 W/cm 2 , 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.

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An adaptive optical system is developed to correct the wavefront of laser radiation distorted by a turbulent air flow. The use of a field-programmable gate array as the main control element makes it possible to achieve a system bandwidth of 2 kHz. The results of experiments on dynamic correction of the phase of a laser beam distorted by a flow of heated air are presented and analysed.