Narrow-linewidth mode-lock figure-eight nanosecond pulse fiber laser

A new figure-eight mode-lock laser design based on a passive nonlinear loop mirror with a small modulation depth has been proposed. Self-started narrow-linewidth nanosecond-pulse lasers are realized: one is based on polarization-insensitive components (with a polarization controller) and the other is an environmentally stable adjustment-free laser based on polarization-maintaining components. In both cases, the lasers generate rectangular-shaped pulses. The duration of the pulses can be continuously adjusted from sub-nanosecond to more than tens of nanoseconds by simply changing the pump power.