In this article, it is demonstrated the generation of high pulse energy, high beam quality and high brightness mode-locked picosecond pulses from a compact Nd:YVO4 master oscillator power amplifier system. This system mainly consisted of a SESAM mode-locked picosecond seed generator and four-stage multi-pass amplifiers. A pulse picker was adopted prior to power amplifiers to efficiently reduce the pulse repetition rate. The maximum average output power of 65.5 W was obtained with a repetition rate of 496.85 kHz and a pulse duration of 16.9 ps, corresponding to a maximum pulse energy of 131.83 µJ and a peak power of 7.8 MW. While simultaneously, the output beam quality factors along the x axis and the y axis were measured to be Mx2=1.36 and My2=1.32, respectively, therefore, a brightness as high as 3.22 × 109 W·cm−2·Sr was achieved. As far as we all know, this is the highest brightness for a picosecond pulsed Nd:YVO4 MOPA laser at 1064 nm.

Hollow-core negative-curvature fibres have been the focus of current research, but how to reduce the loss of hollow-core negative-curvature fibres is a serious problem. This paper proposes a new structure of hollow-core negative-curvature fibres, that is numerically simulated using the finite-element method, and compared with the simulation results of hollow-core conjoined-tube negative curvature fibres (CTNCFs) and hollow-core nested anti-resonant nodeless fibres (NANFs). The results show that, the LP 01 mode loss can reach 0.003694 dB/km with a transmission wavelength of 1.06 μm, the LP 11 mode loss can be as low as 0.28423 dB/km, and the bending loss is 0.4405 dB/km with a bending radius of 5 cm and a transmission wavelength of 1.06 μm. The loss is reduced by an order of magnitude compared to CTNCFs and NANFs.

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