Numerical simulations of 1 kHz, high-energy, broadband multipass amplification for a Ho:YLF chirped pulse amplification system

We demonstrate the high-gain of two double-pass Ho:YLF amplifiers with high-energy seed pulses injection via a modified population inversion Frantz-Nodvik model by numerical simulation. From the numerical simulation results, 26.2 mJ/1 kHz amplified pulses can be obtained by two double-pass amplifiers with 20 μJ/1 kHz, 40 nm (FWHM) bandwidth seed pulses injection. Due to ~1300 gain, the bandwidth of the amplified pulse decreases to about 3.5 nm (FWHM), corresponding to 466 fs pulse duration near 2 μm wavelength. Therefore, the spectrum shaping of seed pulses is induced to suppress the gain narrowing effect. Then, the pulses can be amplified to 22.8 mJ with a spectrum of 16 nm (FWHM), which supports 368 fs pulse duration near 2 μm by simulation.