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Advances in High-Power Green Laser Research and Its Applications in Copper Material Processing (Invited)
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DOI：10.3788/LOP252336.png)
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Abstract
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Significance Copper, renowned for its exceptional electrical and thermal conductivity, is indispensable in manufacturing sectors such as new energy vehicles, aerospace, and electronic communications. However, its extremely low absorption rate (--5 degrees 0) of conventional 1064 nm near-infrared (IR) laser radiation leads to major processing challenges, including low efficiency, significant heat-affected zones, and poor quality stability. This has been a critical bottleneck restricting technological advancement in these fields. The emergence of high-power green lasers (wavelength of 515 - 535 nm), offering a dramatically increased absorption rate in copper (--40 degrees 0), presents a revolutionary solution. By fundamentally altering the laser-material interaction, green lasers enable efficient, high-precision, and low-damage processing of highly reflective copper materials, thereby unlocking new potentials in electric vehicle battery manufacturing, precision electronics, and additive manufacturing. Progress This review systematically elaborates on the technological principles, developmental milestones, and industrial applications of high-power green fiber lasers. The core advantage stems from the wavelength-dependent absorption mechanism in metals. Compared to IR lasers, green lasers achieve approximately an 8-fold increase in absorption of copper, which significantly reduces required power input, minimizes thermal effects, and suppresses spatter and porosity formation during welding. The absorption rate of copper for green light remains stable across a wide temperature range, avoiding the abrupt changes seen with IR lasers that can destabilize the melt pool. The evolution of high-power green lasers is built upon two key technological pillars: high-power, narrow-linewidth, single-frequency fiber lasers and efficient frequency-doubling techniques. Advances in narrow-linewidth fiber lasers have focused on suppressing nonlinear effects like stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) to scale up power while maintaining beam quality. Techniques such as phase modulation (e. g., pseudo-random binary sequence and white noise sequence modulation) have been pivotal in achieving kilowatt-level, diffraction-limited output from single-frequency seeds. Concurrently, frequency-doubling technology has progressed from intracavity schemes in solid-state lasers to external single-pass doubling using critically phase-matched LBO crystals. The latter, combined with high-brightness fiber laser sources, has become the mainstream approach for industrial high-power green laser generation, offering an optimal balance of efficiency, power, beam quality, and stability. Commercially available single-mode green fiber lasers now deliver continuous-wave power exceeding 2 kW with a beam quality of M2 < 1.2. These technological breakthroughs have directly enabled superior processing outcomes for copper. In new energy vehicle battery manufacturing, green laser welding of copper busbars and tabs achieves deep penetration, virtually spatter-free seams, and joint densities exceeding 99.5 degrees 0, critically enhancing battery safety and reliability. In additive manufacturing, green laser powder bed fusion (GL-PBF) of pure copper overcomes the high reflectivity challenge, producing parts with densities exceeding 99. 8 degrees 0, excellent electrical conductivity (>100 degrees 0 IACS), and the ability to fabricate intricate fine features like thin walls and internal cooling channels, which are crucial for thermal management components in aerospace and electronics. Conclusions and Prospects High-power green fiber laser technology has matured into a key enabling tool for precision copper processing, demonstrating clear advantages over IR and blue lasers in terms of absorption efficiency, beam quality, and process stability. Future development is oriented toward three primary goals: higher power, improved beam quality, and smarter process control. The next milestone aims at achieving 5000 W-level single-mode continuous-wave output, which requires overcoming intensified thermal management challenges in frequency-doubling crystals at multi-kW fundamental power levels. Ultrafast pulsed green lasers also hold promise for cold processing of copper but need significant improvements in wall-plug efficiency. Furthermore, integrating intelligent technologies like machine vision for real-time melt pool monitoring and digital twins for process optimization will be essential to enhance processing consistency and expand applications. The application landscape is poised to broaden from its current strongholds in batteries and aerospace into semiconductor packaging, medical device manufacturing, and hydrogen energy infrastructure, driven by the ongoing demand for miniaturization, high performance, and complex geometry fabrication in copper components.
Keywords:
high-power green lasers
high-power narrow-linewidth lasers
copper material processing
laser welding
3D printing
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