Direct amplification of femtosecond optical vortices in a single-crystal fiber
Changsheng Zheng, Tianyi Du, Lei Zhu, Zhanxin Wang, Kangzhen Tian, Yongguang Zhao, Zhiyong Yang, Haohai Yu, Valentin Petrov
Abstract
Spatially twisted light with femtosecond temporal structure is of particular interest in strong-field physics and light–matter interactions. However, present femtosecond vortex sources exhibit limited power handling capabilities, and their amplification remains an ongoing challenge particularly for high-order orbital angular momentum (OAM) states due to several inherent technical difficulties. Here, we exploit a straightforward approach to directly amplify a femtosecond optical vortex (FOV, OAM =−8 ℏ ) by using a two-stage single-crystal fiber (SCF) amplifier system without pulse stretching and compression in the time domain, delivering 23-W, 163-fs pulses at a repetition rate of 1 MHz. The spatial and temporal features are well-conserved during the amplification, as well as the high modal purity (>96 % ). The results indicate that the multi-stage SCF amplifier system is particularly suited for direct amplification of high-order FOVs. The generated high-power femtosecond OAM laser beams are expected to help reveal complex physical phenomena in light–matter interactions and pave the way for practical applications in attoscience, laser plasma acceleration, and high-dimension micromachining.