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An up to 8th order cascaded Raman random fiber laser with high spectral purity is achieved with the pumping of a narrow linewidth amplified spontaneous emission source. The spectral purity is over 90% for all the 8 Stokes orders. The highest output power is 6.9 W at 1691.6 nm with an optical conversion efficiency of 21% from 1062.0 nm. As a comparison, with conventional FBG-based fiber oscillator as pump source, only 47% spectral purity is achieved at 8th order. The temporal stability of the pump laser is proved to play a key role, because the time fluctuation of pump laser is transferred directly to Raman outputs and results in power distribution among different Stokes orders.

589 nm lasers pulsed at Larmor frequency, several hundreds of kilohertz, can increase the brightness of a sodium guide star and are required in remote magnetometry with mesospheric sodium. By amplification of a continuous-wave single-frequency 1178 nm laser in a pulse-pumped Raman fiber amplifier and frequency doubling in an external cavity, high-power pulsed 589 nm laser at Larmor frequency is obtained for the first time, to the best of our knowledge. The pulse format is mainly determined by the 1120 nm Raman pump laser, whose pulse repetition rate and duty cycle are adjustable. Active pulse shaping is applied to minimize the relaxation spike at the leading edge of the pulses. A reduction in pulse width and conversion efficiency from 1120 to 1178 nm is observed in the backwardly pumped Raman fiber amplifier due to the pump pulse transition effect. A 589 nm laser pulsed at a 350 kHz repetition rate and 20% duty cycle with average power up to 17 W is demonstrated as an operation example intended for a geomagnetic field of 0.5 G.