2-µ m, 1.5-mJ, 6.9-ps, near-diffraction-limited CPA-free amplifier based on Ho:YLF crystal

We report on a 2-µ m millijoule-level picosecond amplifier system based on Ho:YLF, operating without chirped-pulse amplification. By implementing in-band pumping and an orthogonal thermal compensation architecture, a maximum pulse energy of 1.5 mJ was obtained at a 1 kHz repetition rate, with a pulse duration of 6.9 ps and an overall gain of 64 dB for the amplifier chain. Near-diffraction-limited beam quality was demonstrated, with M x 2 =1.12 and M y 2 =1.02 along the orthogonal directions. This approach offers an effective route for picosecond pulse energy scaling at 2 µ m without chirped-pulse amplification, enabling millijoule-level output with near-diffraction-limited beam quality.