Amplification of Nanosecond Pulses in a Single- Mode Erbium-Doped Fluoride Fibre Amplifier

We investigate the amplification of nanosecond pulses in a single-mode Er-fluoride fibre amplifier. A PPLN-based optical parametric oscillator (OPO) with a Q-switched Nd:YAG pump laser was used to generate seed pulses at a wavelength of 2790 nm. The OPO system produced seed pulses with sub-10 ns pulse durations and pulse energies of <inline-formula> <tex-math notation="LaTeX">$0.5~\mu \text{J}$ </tex-math></inline-formula> at a repetition rate of 10 kHz. These seed pulses were amplified in a single-mode Erbium-fluoride fibre amplifier, consisting of 2.2 m of double-clad fibre with a doping concentration of 7 mol%. Using this setup, we demonstrate gain values of up to 20 dB, output pulse energies of <inline-formula> <tex-math notation="LaTeX">$52.7~\mu \text{J}$ </tex-math></inline-formula>, and peak powers of more than 8 kW.