Optically addressed liquid crystal light valves for an adaptative control of amplitude and phase of laser beam

Space aberration effects which arise in high energy or in high average power laser chains are important parameters to control in order to emit a beam quality close to the diffraction limit. For that purpose we present recent experiments using an original adaptative and programmable module allowing the spatial control of the beam amplitude and the correction of the phase distortions due to the optical components and the gain media of the laser chain. Beam shaping is achieved by an optically addressed photoconductor-liquid crystal light valve. The light valve is addressed in the blue-green spectral range by incoherent projection of a VGA liquid crystal display. This adaptative optics module controls either the amplitude or the phase of near infrared laser beams depending on the liquid crystal operating mode. The other specific characteristics of the module will be detailed: No spurious diffraction effects, up to 10π phase excursion and tri-lateral wavefront sensor. Experimental results of compensation of aberrations introduced on different laser beams will also be presented.