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 proposed.•The total thermally induced wavefront aberration in the Nd: glass square rod is 0.57 µm, which is reduced by 37% compared to the initial structure.•Liquid induced wavefront is experimental studied.