High-Intensity Nanosecond All-Fiber-Coiled Laser and Extreme Ultraviolet Generation

摘要

High-efficiency fiber-based extreme ultraviolet driver in the alignment-free configuration has been experimentally achieved with a maximum intensity of 6.4×10~(10) W/cm~2 on target at a repetition rate of 20 kHz. The output EUV signal within 10-20 nm in wavelength was confirmed with a Si/Zr-coated x-ray photodiode by varying numbers of Be and Al foil filters. The measured spectral range is consistent with that obtained by the weighted oscillator strengths of Sn~(8+) to Sn~(+13) ions using an one-dimensional hydrodynamic code coupled with the ionization model of collisional-radiative equilibrium. The driver is based on a 1064-nm nanosecond coiled ytterbium all-fiber laser system in diode-seeded master oscillator power amplification. With an overall optical efficiency up to 56%, it can deliver a 1.16-mJ, 117-kW, 6.1-ns laser pulses with a FWHM linewidth of 10 nm and beam propagation factor of M~2～1.55. The full advantages of using fiber laser for a movable LPP EUV metrology source are revealed.