High-Power High Beam Quality Narrow-Linewidth Quasicontinuous Wave Microsecond Pulse 1064-nm Nd:YAG Amplifier

We demonstrated a high average power, high beam quality, narrow linewidth, quasicontinuous wave (QCW) diode-pumped 1064-nm Nd:YAG amplifier. A narrow-linewidth QCW pulse Nd:YAG oscillator was employed as the seed laser, providing a maximum average power of 53.4 W at a pulse repetition frequency of 500 Hz and pulse width of 108 
μ
s with a beam quality factor M
²
= 1.21. After that, a two-stage double-pass Nd:YAG amplifier was performed. The amplifier delivers a maximum output power of 238 W with a linewidth of 0.4 pm and a tunable range of 119.3 pm. The beam quality was measured to be M
²
= 1.65. To the best of our knowledge, this represents the highest average power and the highest brightness for a narrow-linewidth QCW microsecond pulse 1064-nm laser.