Nanosecond Q-switched operation of coupled Yb and Tm fibre lasers

Abstract

A small scale coupled Yb-silica and Tm-sillea fibre laser system is described with output at 1.9 μ m and with Q-switching using an acousto-optic modulator and also by mechanical optical modulation. The Yb-fibre laser pump Source exhibited strong self-pulsation with high-intensity pulses due to stimulated Brillouin scattering. But regular Q-switched pulses were generated from the Tm-fibre laser with an energy of ∼ 2.4 μ J and duration (FWHM) of ∼ 280 ns for modulation frequencies of 1-20 kHz when using acousto-optic modulation. The main effects that limit the Q-switched Pulse peak power are the onset of gain-switched pulsing during, the low-Q state and strong pump excited state absorption.