Development of wavefront control system using deformable mirror for solid state lasers

The correction of wavefront distortion of laser beams propagating through laser media and optics is a key issue for developing high quality and high average power solid state lasers especially for ultra short high peak power lasers. For this purpose, we have been developing a closed loop wavefront control system composed of a Shack-Hartmann type wavefront sensor, personal computer, diagnostic computer and deformable mirror. We used two kinds of deformable mirrors, one of which is a Stacked Array type Mirror (SAM) with 52 actuators, and the other of which is a Bimorph type Mirror (BIM) with 13 electrodes. In the system, the phase-conjugate wavefront surface measured by the Shack-Hartmann type wavefront sensor is directly reconstructed on the deformable mirror. The response bandwidths of the control loop are 8.7 Hz for SAM and 13.5 Hz for BIM. In both cases, the Root Mean Square (RMS) of wavefront distortion is reduced to less than 1/5 of original aberration of He-Ne laser. By applying SAM to solid state laser, the RMS of the wavefront distortion is reduced to 0.041 mu m from 0.12 mu m.