Beam wavefront dynamical compensation by aberrations of the gain medium in laser amplifiers for beam quality...

A method is presented to dynamically improve the beam quality in laser amplifiers by spherical aberration compensation. By imaging the field with a negative spherical aberration into a laser amplifier, the wavefront aberration of an input beam could be compensated by that of the gain medium in the amplifier with positive spherical aberration. Both power amplification and beam quality improvement can be achieved simultaneously. No additional optical components are introduced. Experiments are conducted for a beam from an oscillator with 28 W output power. The M2 factor of the beam was improved from 4.2 to 1.6 after amplification. The power was also amplified to 54.7 W. It is a cost-effective and passive way for wavefront compensation, as compared to deformable mirrors and phase corrector plates.