20 kW Monolithic Fiber Amplifier With Directly Dual-Wavelength Laser Diodes Counter Pumping

In this study, we demonstrate a high-power ytterbium-doped fiber laser (YDFL) based on laser diodes (LDs) directly pumping scheme. Tandem pumping and LD direct pumping are two common schemes for generating high-brightness laser output in YDFL. Compared to tandem pumping, LD direct pumping scheme has prominent advantages such as high efficiency, small size, and low cost. Therefore, it has a significant competitive advantage in industrial applications. We report a 20.27 kW monolithic fiber amplifier with directly dual-wavelength LDs counter pumping. The fiber amplifier emitting at 1080 nm has an optical-to-optical efficiency of 84.8%. The Raman intensity is more than 50 dB lower than the signal light intensity. By optimizing the design of YDF and components, the output power and beam quality of the laser can be further enhanced.