396-MHz 1030-nm hybrid CPA amplifier based on fiber-Yb:YAG crystal thin rod

The paper presents the design of a high repetition frequency, high-energy femtosecond laser system for industrial processing. For the first time, we employed a hybrid chirped-pulse amplification (CPA) system based on 396 MHz high repetition frequency femtosecond pulses generated from optical fiber and thin rod Yb:YAG crystals. The ultrashort pulsed all-fiber front-end pulse train was chosen at 25 kHz, resulting in an average output power of 13.76 W. The output laser had a central wavelength of 1030 nm with a spectral width of 3.5 nm. The compressed pulse width was measured to be 791 fs, and the pulse train energy reached 550 μJ. The linearly polarized ultrashort pulsed laser exhibited excellent power stability of 0.49%. The beam quality was characterized by M_x²=1.21 and M_y²=1.23. It is worth noting that the combined use of optical fiber and crystal rods in the amplifier structure effectively mitigates the strong nonlinear effect of the optical fiber on peak power enhancement. The femtosecond laser system demonstrates remarkable features, including high repetition frequency, high burst energy, high power stability, superior spot quality, as well as cost-effectiveness and reliability. Therefore, it is deemed to be an ideal choice for femtosecond laser applications in the field of ultrashort pulse industrial processing.