Old Wavelength, New Performance: Hectowatt 200-Μj-level Femtosecond Fiber CPA System at 1064 Nm

The Yb:fiber based high-power and high-energy ultrafast lasers usually feature central wavelength of 1030 nm instead of the more common one of 1064 nm, thus limiting some potential wavelength-dependent applications. In this work, a hectowatt 1064-nm femtosecond chirped pulse amplification (CPA) system based on double-stage rod-type photonic crystal fiber (PCF) amplifier was demonstrated, with a pulse energy of 212-μJ and a repetition rate of 0.5 MHz. Compared with our previous work [Opt. Express 30(6), 3611, 2022], two key measures were employed. Firstly, a Yb:YAG crystal was intentionally introduced as a spectral filter for avoiding 1030-nm amplified spontaneous emission (ASE) oscillation, which hence improved the signal-to-noise ratio (SNR) by 15 dB. Secondly, an additional stage of rod-type PCF amplifier was adopted for further power scaling, achieving an average power of 127 W. Finally, the pulse was compressed to ∼460 fs, with an average power of 106 W and a compression efficiency of ∼83%. The beam quality factors (M2) were measured to be M2 X = 1.12 and M2 Y = 1.09. To the best of our knowledge, this is the highest pulse energy among 1064-nm hectowatt-level femtosecond lasers, thus providing a high-quality source for wavelength-dependent applications. For example, it can be used as a driver for high-repetition-rate vacuum ultraviolet (VUV) sources about 10.5 eV, with an expected conversion efficiency of up to 1%.