Gain-switching pulse generation of Tm-doped fiber ring laser pumped with 1.6-µm laser diodes

We present a Tm-doped fiber laser operating around 1.9 μm by bi-directional pumping with 1.6 μm-band laser diodes. The laser output pulse is built by using a gain-switching pump pulse with a bias pump pulse. The output pulse power is measured to 119 mW when the bias pump power and the gain-switching pulse power are 71.7 and 46.6 mW, respectively. The output power is changed by tuning the feedback ratio of the variable-ratio output coupler and maximized at the feedback ratio of 0.81. The laser wavelength varies from 1.88 to 1.92 μm depending on the length of the Tm-doped fiber.