Neodymium:YAG active mirror for the amplification of mode-locked laser pulses

To meet the need for higher-average-power laser ranging transmitters, the authors designed and tested the first Nd:YAG active mirror amplifier. The advantages of an active mirror amplifier geometry are threefold. First, with the mirror geometry, large apertures are possible with the presently available crystals of Nd:YAG. Large apertures are essential to avoid damage and beam distortions that occur at high-peak intensities. Second, thermal birefringence and thermal lensing are eliminated by having the laser propagate parallel to the thermal gradients in the mirror. Areas near the mirror's edges where the gradients are nonuniform can be simply avoided. The Nd:YAG active mirror amplifier should have crystal stress fracture-limited average power capability without restriction to linear laser polarization