60.4 W continuous-wave single-frequency laser output from a two-stage Nd:YAG single-crystal fiber amplifier

A Nd:YAG single-crystal fiber amplifier for the amplification of continuous-wave single-frequency laser end-pumped by a laser diode (LD) is investigated. With a two-stage amplification configuration, an output power of 60.4 W under the total incident pump power of 200 W is achieved, which is, to our knowledge, the highest power from a continuous-wave single-frequency laser achieved with a single-crystal fiber scheme. The extraction efficiency reaches 41.6% in the second amplification stage, which is comparable with Innoslab amplifiers. The beam quality factors M² at the maximum output power in the horizontal and vertical direction are measured to be 1.51 and 1.38, respectively. The long-term power instability for 1 hour is 0.97%.