Saturable absorber based on graphene for a hybrid passive mode-locked erbium-doped fiber laser

Abstract

We proposed a hybrid passive mode-locked fiber laser based on a saturable absorber fabricated by coating a layer of graphene on a single-mode fiber with inscribed short waveguides. The hybrid mode-locked fiber laser operation is achieved by use of nonlinear polarization rotation and saturable absorption. The output pulses have the center wavelength of 1558 nm, 3-dB bandwidth of 4.6 nm, pulse width of 605 fs, repetition frequency of 20.8 MHz, and signal-to-noise ratio of 60 dB. Compared with the use of nonlinear polarization rotation mode locking alone, the pulse width is compressed by 211 fs, and the signal-to-noise ratio is improved by 5 dB. The advantages of hybrid mode locking mechanism include simple structure and convenient operation, which make the system attractive in ultrafast lasers.