Recently, Assistant Professor Dong Zhipeng and colleagues from Xiamen University's School of Electronic Science and Technology published groundbreaking research in Advanced Photonics Nexus.
By ingeniously employing phase-bias technology, they extended the operational range of ytterbium-doped mode-locked lasers into the long-wavelength region, achieving stable mode-locked pulse output at 1120 nm-the longest wavelength directly emitted by ytterbium-doped mode-locked fiber lasers to date. This work offers a novel solution for obtaining high-power, highly stable ultrafast yellow-green laser sources, with broad application prospects in biomedical and industrial processing fields.
The research team designed a resonator based on phase-biasing technology, integrating gain tuning and wavelength selection within the cavity to ensure reliable operation at the target wavelength. The introduction of phase-biasing significantly lowers the mode-locking threshold, enabling reliable self-initiation and sustained stable mode-locking over extended periods. Furthermore, high-concentration ytterbium-doped fiber was selected as the gain medium to achieve gain spectrum redshift. All optical components-including wavelength division multiplexers and fiber gratings-were optimized for the 1120 nm wavelength, maximally suppressing losses in this band to ensure reliable operation at 1120 nm.
Based on this sophisticated design, the laser directly outputs stable mode-locked pulses at 1120.06 nm, setting the longest wavelength record for this type of laser. To achieve higher power, the team employed a master oscillator power amplifier (MOPA) structure for amplification, reaching a maximum output power of 1.39 W while maintaining excellent beam quality and spectral purity. Furthermore, by employing LBO crystals for frequency doubling, the team successfully generated an ultrafast yellow-green laser with a center wavelength of 560.03 nm and a maximum output power of 457.88 mW. This demonstrates the immense potential of this laser source as a practical yellow-green light source.
