Abstract:
Background Tandem pumping scheme is commonly employed for high power fiber laser systems, where the 1 018 nm fiber laser serves as the most prevalent pump source. However, the output power of monolithic 1 018 nm fiber lasers is limited to 1 kW level due to the amplified spontaneous emission (ASE) effect. This limitation necessitates the use of a large number of these pump sources in tandem-pumped fiber laser systems, resulting in bulky and complex configurations.
Purpose This paper presents a modeling and optimization framework for scaling the power of 1 018 nm fiber lasers.
Methods The framework, built upon the beam propagation method and broad-spectrum rate equations, targets the optimization of critical parameters to strategically balance laser efficiency against signal-to-ASE ratio.
Results Guided by the framework, a bidirectional pumping scheme was employed alongside an optimized fiber coil diameter, which effectively suppressed both ASE and the transverse mode instability. This approach enabled a monolithic output power of 1.94 kW at 1 018 nm, with an optical-to-optical efficiency of 76.38%, a signal-to-ASE ratio of 33.22 dB, and a beam quality factor M2 of 1.91.
Conclusions By achieving a monolithic 2-kW 1 018 nm laser, this work improves the compactness and integration level of high-power fiber lasers with tandem pumping scheme, thus enabling future breakthroughs in the power and brightness scaling of tandem-pumped fiber lasers.
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