High power all-fiber laser with switchable pulsed and continuous operation modes for wind lidar

We have designed and demonstrated an all-fiber laser which can switch the operation mode between the pulsed mode and the continuous mode. Under the pulsed operation mode, the maximum output pulse energy is measured to be 120 μJ with a pulse width of 400 ns. The pulse width is continuously adjustable between 100 ns and 600 ns. Under continuous operation mode, the maximum output power is 2 W. Switching between these two operation modes can be done with simple instructions within several milliseconds. Large-mode-area (LMA) fiber amplifiers are adopted to support the high peak power. The LMA fiber amplifiers are coiled in a circle with a diameter of 25 cm and the high order transverse mode are suppressed by the bending loss. The M squared factors of the designed laser are 1.204 on x-axis and 1.293 on y-axis. This laser is optimized for coherent Doppler lidar system that can detect at both the near (within several tens of meters) and far distance (more than a dozen kilometers).