Efficient high-harmonic generation from a stable and compact ultrafast Yb-fiber laser producing 100 micro-joule, 350 fs pulses based on bendable photonic-crystal fiber

摘要

The development of an Yb3+-fiber based chirped-pulse amplification system and the performance in the generation of extreme ultraviolet (EUV) radiation by high-harmonic generation is reported. The fiber laser produced 100 µJ, 350 fs output pulses with diffraction limited beam quality at a repetition rate of 16.7 kHz. The system used commercial single-mode, polarization maintaining fiber technology. This included a 40 µm core, easily packaged, bendable final amplifier fiber in order to enable a compact system, to reduce cost, and provide reliable and environmentally stable long term performance. The system enabled the generation of 0.4 µW of EUV at wavelengths between 27-80 nm with a peak at ~45 nm using xenon gas. The EUV flux of ~10^11 photons per second for a driving field power of 1.67 W represents state-of-the-art generation efficiency for single-fiber amplifier CPA systems, corresponding to a maximum calculated energy conversion efficiency of 2.4 x 10-7 from the infra-red to the EUV. The potential for high average power operation at increased repetition rates and further suggested technical improvements are discussed. Future applications could include coherent diffractive imaging in the EUV, and high-harmonic spectroscopy.