Pulse amplification in a Cr4+:forsterite single longitudinal mode (SLM) multi-pass amplifier

An efficient multi-pass Cr:forsterite master oscillator-power amplifier laser system operating in the single-longitudinal mode was demonstrated and characterized. A significant increase in energy was obtained in a six-pass amplifier configuration giving a maximum value of up to 10.8 mJ, with a good beam quality and without significantly broadening the linewidth or increasing the M2. The amplifier performance was evaluated as a function of the pump energy and the number of passes. A Fourier transformation of the laser pulses was performed to confirm the linewidth value measured using a Fabry-Perot etalon.