A long pulse width neodymium-doped glass rod laser amplifier with a moving input laser beam

A method is developed for reducing the thermal self-focusing effect in a long pulse width Nd glass laser amplifier with a moving input laser beam. The input laser beam is rotated around a fixed point of the rod axis at a high rotating speed which is equivalent to smoothing the spatial distribution of the time-averaged energy density. This method is found to increase the damage threshold within the rod by a factor greater than two while significantly increasing the brightness of the amplified output laser beam.