1.7 μm all-fiber figure-9 mode-locked laser based on a fiber Bragg grating

Abstract

Abstract Fiber lasers operating at 1.7 μm have very important applications in biomedicine, optical imaging, laser welding, optical communication and other fields because of their rich spectral characteristics in the near-infrared band. We designed and experimentally implemented a 1.7 μm all-fiber figure-9 (F9) mode-locked laser, with a fiber Bragg grating (FBG) acting as both the mirror and the spectrum filter. The all-fiber F9 design made the laser work in the mode-locking state more efficiently. We obtained mode-locked pulses with a central wavelength of 1724.76 nm and a repetition rate of 14.39 MHz when the pump power was 1.1 W, and the pulse width was about 54 ps. Limited by the bandwidth of the FBG, the 3 dB bandwidth of the mode-locked spectrum was about 0.18 nm. The output power was 52 mW at a pump power of 2.5 W. The multi-pulse dynamics were studied by adjusting the pump power and the polarization controllers, and pulse trains of up to six pulses in a group were achieved. The 1.7 μm narrow-bandwidth all-fiber F9 mode-locked laser is simple in structure and easy to build, with potential application as a seed source in high-energy ultrashort pulse lasers.