Abstract:
Background Single-frequency fiber seed sources with high output power and low intensity noise are critical for laser-driven inertial confinement fusion drivers and high-power fiber laser systems, as they directly affect beam power balance, temporal waveform quality, and beam combination efficiency.
Purpose This study aims to investigate power scaling and intensity noise suppression in a distributed Bragg reflector (DBR) single-frequency Yb-doped fiber laser to meet the demanding requirements of these applications.
Methods For power scaling, two DBR lasers are constructed: a 1053 nm laser with a gain fiber length of 6.5 mm and a low-reflectivity FBG reflectivity of 74%, and a 1064 nm laser with a gain fiber length of 10.5 mm and a low-reflectivity FBG reflectivity of 55%. Their output power characteristics are compared. For intensity noise suppression, an optoelectronic feedback loop combined with a semiconductor optical amplifier (SOA) is applied to the 1053 nm laser.
Results The results show that the 1064 nm laser achieves an output power of 197.3 mW under 800 mW pump power with a slope efficiency of 24.45%, a significant improvement over the 1053 nm laser (29.7 mW under 600 mW pump power, slope efficiency 5.12%). After noise suppression, the relaxation oscillation peak amplitude drops from -99 dBc/Hz to -120 dBc/Hz, achieving a 21 dB suppression, and the relative intensity noise across the entire frequency band is reduced by approximately 10 dB, reaching a level lower than that of a commercial foreign laser.
Conclusions These results demonstrate that increasing gain fiber length while maintaining single-longitudinal-mode operation and appropriately reducing low-reflectivity FBG reflectivity is an effective approach for power scaling, and that the combination of optoelectronic feedback and SOA provides significant suppression of intensity noise across a broad frequency range.
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