High Energy Sub-kHz Linewidth Pulsed Single-Frequency Fiber Laser

A high energy and sub-kilohertz pulsed single-frequency laser is demonstrated with an all-fiber master oscillation power amplification scheme. A polarization-maintaining large mode area tapered ytterbium-doped fiber is utilized in the main amplification stage for mitigating the unwanted nonlinear Brillouin effect. In addition, synchronized pulse pumping is employed to suppress the amplified spontaneous emission effect during the amplification of laser pulse with low repetition rate, while seed pulse temporal pre-shaping is adopted to compensate for waveform distortion of a long pulse. As a result, a high-performance pulsed laser with 653 Hz linewidth and maximum pulse energy of 369 mJ at a repetition rate of 100 Hz is realized. The duration of the recorded rectangle pulse is 1.1 ms, corresponding to an estimated peak power of 335.5 W. At the maximum output power, the M² factor of the collimated output beam is assessed to be 1.25. It is believed that the obtained results represent the highest energy and narrowest linewidth ever reported for pulsed single-frequency fiber lasers.