High power supercontinuum generation with 70 W average output power in a nonlinear ytterbium-doped fiber amplifier is demonstrated using all-normal dispersion, all-fiber master oscillator power amplifier configuration. The supercontinuum covers from 1064 nm to beyond 1700 nm with spectral flatness better than 12 dB and 67.3% optical to optical conversion efficiency. The almost uniform spectral power density across the whole continuum is more than 70 mW/nm and the nanosecond bursts output have an effective peak power of 82.7 kW.
"Although much progress has been made on improving the splicing and mode field matching between PCF and active fibers, special handling processes are requisite to minimize the splicing loss in the manner of mode field adapters or bridge fibers , , . Recently, near-infrared SC from 1.06 to 1.70 μm was generated in a nonlinear fiber amplifier (with no PCFs) yielding 250 μJ pulse energy and 3 ns duration, but no visible light was observed –. There is still a challenge to widely extend the spectrum of high-power laser sources in all-fiber configuration other than PCFs. "
[Show abstract][Hide abstract] ABSTRACT: We experimentally demonstrated high-power yellow and near-infrared laser emissions by cascaded four-wave mixing in a nonlinear Yb-doped multimode fiber amplifier, generating 2.0 W at 830 nm and 0.35 W at 594 nm. Moreover, multiple cascaded four-wave mixing processes which generated supercontinuum covering more than four octaves from 398 to 1700 nm was also investigated in Q-switched mode-locking regime. The group velocity match-ing for pump and parametric waves as well as multimode fiber amplification promoted the cascaded nonlinear frequency mixing processes. Index Terms—Doped fiber amplifier, fiber lasers, four-wave mix-ing, supercontinuum generation.
IEEE Journal of Selected Topics in Quantum Electronics 09/2014; 20(5). DOI:10.1109/JSTQE.2013.2286077 · 2.83 Impact Factor
"For an all-fiber-structured nanosecond SC source, the SC averaged power spanning from 1064 to 2200 nm has previously been scaled up to 200 W at 3 ns and 1.31 MHz with optical efficiency of 54.6%  using a fiber MOPA system seeded by a mode-locked fiber ring laser. It has been shown that the highest SC peak power spanning from 1064 nm to greater than 1700 nm is up to 82.7 kW  at 3 ns and 281.5 kHz with about 0.25 mJ in energy and 67.3% in optical efficiency using a nonlinear fiber amplifier in the MOPA configuration. "
[Show abstract][Hide abstract] ABSTRACT: In an all-polarization-maintaining-fiber master oscillator power amplifier system at 1064 nm under all normal dispersion, intense nanosecond emission was generated with spectral broadening from 980 to 1600 nm. In such a fiber nonlinear power amplifier, efficient power scaling is able to be free from significant depletion because both laser amplification and nonlinear conversion are simultaneously employed. As a result, output peak power up to 117 kW with a pulse energy of 1.2 mJ is generated with a maximum core intensity of 30 GW cm−2. In addition, the conversion efficiency is 66% for a pulse duration of 6.1 ns at the moderate repetition of 20 kHz. The output level is close to the damage threshold for long-term operation. The onset and interplay of constituted fiber nonlinearities can be addressed, especially from single mode to a few modes, stage by stage. Furthermore, the seeding influence on the spectral broadening reveals its versatility for enabling many potential applications. For seeding by a highly controlled diode laser at the nanojoule level, a double-pass preamplifier significantly improves the energy extraction, resulting in a high input level for an efficient nonlinear power amplifier. Such a linearly polarized light source composed of an intense 1064 nm pump and a broad sideband seed is beneficial for efficiently driving broadband tunable optical parametric amplification.
"the record-high outputs were reported for averaged power of 200 W , and peak power and energy up to 82.7 kW and 0.25 mJ , respectively. However, in the references of that using a highly-nonlinear passive PCF, the maximum averaged power is only around 50 W  owing to a total coupling efficiency of around 40% and the maximum pulse energy is merely 0.04 mJ . "
[Show abstract][Hide abstract] ABSTRACT: High power fiber laser amplifier cascade can be simplified using double-pass scheme due to improvement of overall efficiency, especially for amplifiers with small input seed or high stored energy. The yield of stimulated Raman scattering (SRS) in the double-pass scheme is comparable to the level in amplifiers using counter-directional-pumped single-pass scheme if the pumping configuration is appropriate, even though the interaction length becomes twice for double pass scheme. In the study, insertions of Raman strippers along the active fiber with double-pass scheme is proved to be another choice to effectively suppress SRS besides the utilization of photonic band-gap fibers.
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