We demonstrate an all-fiber picosecond laser with a repetition rate of 1.2 GHz. The seed source is a passively modelocked Yb-doped fiber laser. The pulse width of the seed laser is 4.2 ps with a repetition rate of 19.2 MHz, and the seed exhibits a spectral bandwidth of 3.6 nm at the center wavelength of 1064.1 nm. Due to the length of the cavity, it is difficult to increase the repetition rate of the fiber laser. To solve the above problem, we provide a high-repetition-rate pulsed laser modulator comprising: five 2 × 2 type, splitting ratio 50:50 couplers, two 1 × 2 type, splitting ratio 50:50 couplers, to increase the repetition rate of the seed laser to 1.2 GHz. Meanwhile, the novel combination of the devices can realize a low-loss mutual coupling of laser pulses.
Amplification of low-power pulsed single-frequency fiber laser operating at 1064nm has been theoretically investigated. A single-mode Ytterbium doped fiber (YDF) is pumped by a 980nm CW laser. The seed laser has a peak power of 10mW, repetition rate of 65kHz and pulse width of 7ns. Considering the gain of ASE, the optimal length of YDF is around 0.6m when the system operates with the doping concentration of Ytterbium ions of 10<sup>26</sup>m<sup>-3</sup>, core radius of 3μm, numerical aperture of 0.11 and pump power at 0.3W.