All fiber-based single-frequency Q-switched laser pulses at 2 μm for lidar and remote sensing applications

We report an all fiber-based single-frequency Q-switched 2 μm pulsed laser based on highly Tm-doped germanate fiber by using a piezo to induce stress in fiber laser cavity. The pulse width of this Q-switched fiber laser can be tuned from 10's ns to sub-μs. The repetition rate can be tuned from 100 Hz to 100's kHz. The average power is ~ mW-level, peak power wattlevel, and pulse energy 30-75 nJ without any amplifier. Moreover, this transform-limited fiber laser pulses has been scaled up to 220 μJ by using a newly developed SM PM highly Tm-doped germanate fiber 25/250μm for transform-limited 80 ns pulses at repetition rate 20 kHz. This narrow linewidth high energy MOPA-based pulsed fiber laser can be used for LIDAR and laser remote sensing.