High-power CW and ultrafast laser amplifier operation of a segmented YAG/Yb:YAG/YAG single-crystal fiber grown by a one-step LHPG technique

Single-crystal fibers (SCFs) exhibit a significant potential for high-power laser applications owing to their superior thermal management capabilities. To enhance pump power and mitigate damage at the injection end of SCFs, a segmented YAG/Yb:YAG/YAG SCF with a diameter of ∼200 μm was directly grown using a one-step laser-heated pedestal growth (LHPG) method. The crystallinity and uniformity of the as-grown fiber were evaluated through a real-time back-reflection Laue camera system. Employing a low-loss segmented YAG/Yb:YAG/YAG SCF as the laser gain medium, investigations were conducted on both continuous-wave (CW) oscillators and ultrafast pulse amplifiers. The CW laser operation at 1030.9 nm achieved a maximum output power of 117.6 W with a slope efficiency of ∼46 % , while the ultrafast amplifier system generated pulses with an average power of 101.2 W at a repetition rate of 30.8 MHz. To the best of our knowledge, this represents the highest average power achieved from a single-stage amplifier based on an Yb:YAG SCF. Preliminary pulse compression was performed at a signal power of 50.6 W using a grating pair, resulting in a compressed pulse width of 786 fs with a compression efficiency of 58%. This study highlights the potential of crystal fiber lasers for a new generation of high-power laser systems.