Experimental study of double-pass power amplifier

In a double-pass amplifier system, a laser pulse width(FWHM) of l6.9 ns and more than 216 mJ was obtained in the case of 10 Hz repetition frequency. Furthermore, 203.4 mJ per pulse was achieved where the repetition rate is up to 400 Hz. The beam quality factor is no more than 5 in the case and self-oscillating was successfully eliminated in experiments. But the distribution of laser section is asymmetric, and the reason was theoretically analyzed. HR mirror replaced by phase conjugated mirror and ocillating output mirror by sup-Guass mirror can improve the beam quality.