A 203 µJ, 148 fs Femtosecond Burst-Mode Fiber Laser at 1 kHz

We report a high-energy femtosecond burst-mode laser based on an all-fiber chirped-pulse amplification (CPA) chain followed by a grating compressor. The system incorporates a nonlinear amplifying loop mirror oscillator, a dispersion-adjustable dual chirped fiber Bragg grating stretcher, a fiber-coupled acousto-optic modulator, and three stages of fiber amplification. Temporally synchronized pulsed pumping is applied to the booster and main amplifiers to confine gain buildup to the burst-amplification window, limiting amplified spontaneous emission and unnecessary thermal loading. At a repetition rate of 1 kHz, the system delivers a single-pulse energy of 128 µJ and a total energy of 203 µJ in the three-pulse burst mode. After compression, a pulse duration of 148 fs is obtained, compared with a Fourier-transform-limited duration of 135 fs. The system operates without active cooling and maintains near-diffraction-limited beam quality with M2 = 1.15. To the best of our knowledge, this represents the first demonstration of a flexible Yb-doped fiber CPA system simultaneously combining few-pulse burst operation with a 200 µJ burst energy and a sub-150 fs pulse duration.