2.4-W Narrow-Linewidth Q-Switched $\hbox{Tm}^{3+}$ -Doped Double-Clad Fiber Laser

A narrow-linewidth 793-nm diode-pumped Tm³⁺ -doped double-clad silica fiber laser operated at 2 μm and actively Q-switched with an acousto-optic modulator is reported. Using a fiber Bragg grating as an output coupler, approximately 0.1-nm linewidth at 1996.8-nm pulses is derived at 80-kHz repetition rate. The maximum average output power is above 2 W for 11.6-W absorbed pump power. Less than 150-ns pulse is obtained at the repetition rate of 30 kHz. The laser is a promising seed laser for amplification in a master oscillator power amplifier system.