Diode-end-pumped All-Liquid-cooled Square Rod Nd: Glass Amplifier with Sub-Joule Energy Extraction and Ultralow Thermal Induced Wavefront

A diode-end-pumped all-liquid-cooled square rod Nd: glass eight-pass amplifier is reported. Amplification energy of 700 mJ under a single-pass small signal gain of 2.36 and input energy of 6.5 mJ at a 1 Hz repetition rate and at 9 J pump energy is achieved, corresponding to an effective energy-extraction efficiency of 25.6%. The total single-pass thermally induced wavefront is measured to be 0.57 mu m (peak to valley). To the best of our knowledge, this is the first demonstration of an all-liquid-cooled sub-joule-level square rod Nd: glass amplifier. By optimizing the flowing fluid, the near-field spatial intensity modulation at the maximum energy is 1.38 and 91.6% of the far-field energy is concentrated at three times the diffraction limit.