We report on an all-fiber 200 W widely tunable GHz electro-optic (EO) frequency comb operating in the nonlinear regime. The EO comb pulses at 1030 nm are initially pre-compressed to sub-2 ps, then power amplified to 2.5 W, and finally boosted to 200 W in a newly designed large-mode-area, Yb-doped photonic crystal fiber. Continuously tunable across 12-18 GHz, the picosecond pulses experience nonlinear propagation in the last amplifier, leading to output pulses compressible down to several hundreds of femtoseconds. To push our system deeper into nonlinear amplification regime, the pulse repetition rate is further reduced to 2 GHz, enabling significant spectral broadening at 200 W. Characterization reveals sub-200 fs duration after compression. The present EO-comb seeded nonlinear amplification system opens a new route to the development of high-power, tunable GHz-repetition-rate, femtosecond fiber lasers.
Silica bers have been successful used to deliver high-power high-energy laser beam in the near-infrared and visible range but suffer from high absorption and color formation in the UV spectrum which disqualify then for such wavelength. Recently, the advances of inhibited-coupling hollow-core photonic crystal bers made them as an unique tool to transport UV radiation thanks to an ultralow overlap with the silica cladding and record losses down to 10 dB/km. By further optimizing such ber, we report in this letter a record single-mode delivery of 23.3 W (155 μJ) with 92% transmission from a 343 nm, 10 ns, 150 kHz laser source, corresponding to an improvement of the current state-of-the-art by two orders of magnitude.
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