This paper proposes and verified a modified cavity configuration in oscillating-amplifying integrated fiber laser for stimulated Raman scattering suppression. A short segment of YDF and a long piece of GDF is used in the oscillating section, which can simultaneously suppress the onset of Raman component and avoid the self-pulsing operation caused by the extremely low gain in cavity. Experimental result shows a 31dB Raman suppression ratio at 1080nm when output power reaches 5kW without any other Raman suppression element.
This paper comprehensively considers the suppression effect of fiber parameter control on Stimulated Brillouin Scattering (SBS), and studies the influence of different phase modulation modes, different linewidths, different fiber Yb ion densities, and different fiber lengths on the SBS threshold of the whole system, The best system setting scheme for improving SBS threshold is also given.
The stimulated Brillouin scattering (SBS) effect in fiber amplifiers using white noise signal (WNS) phase modulated seed is simulated. The influences of cut-off frequencies of WNS and the output fiber structure on SBS threshold are discussed. Basing on simulation results, optimized phase modulation signal and output fiber structure are achieved to suppress SBS. A fiber laser is established according to the simulation results.
A direct diode-pumped all-fiber-integrated fiber laser based on backward pumping master oscillator power amplifier configuration at 1080 nm, producing maximum output power of 4.115 kW based on 25/400 μm fiber with corresponding linear fitting optical to optical efficiency of 78.39% was demonstrated. The suppression ratio of stimulated Raman scattering is better than 35dB and it can be further optimized by decreasing the seed input power. Near diffractionlimited beam quality (M2 are 1.7and 1.6 in the x and y directions based on 4-sigma method) is also achieved at the maximum output power. To the best of our knowledge, this is the first report for 4 kW near-diffraction-limited fiber lasers based on 25/400 μm fiber directly pumped by laser diodes.
In this manuscript, a 3.53kW average output power all-fiber laser system at 1064nm with 3dB linewidth as narrow as 0.16nm and near single-mode beam quality (M2 ≈1.7) is demonstrated. There is no obvious stimulated Brillouin scattering, stimulated Raman scattering or amplified spontaneous emission observed. To the best of our knowledge, this is the highest output power of all-fiber laser system with narrow-linewidth and near single-mode beam quality ever reported.
The laser induced micro/ nano-meter size surface structures are fabricated by multi linear polarized femtosecond laser pulses (pulse duration τ=35 fs, wavelength λ=800 nm) irradiation at room temperature(25 ℃ ) and 400 ℃. The structures fabricated at these two temperatures show distinct temperature dependence. The grooves, which are parallel to the polarization of the laser light, can be clearly observed at almost all the structured area formed at 400 ℃ while laser induced period structures(ripples) are the most pronounced surface structure in the crater formed at room temperature. The crystallinity of these surface structures are investigated by using Raman spectroscopy. The Raman spectrum shows that all the structured area formed at 400 ℃ is crystalline(or poly-crystalline) while amorphous silicon can be observed within the structures formed at room temperature (25 ℃). These results indicate that temperature is an important parameter to be tuned to tailor the micro/nano-structure fabrication.
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