Harmonically mode-locked Er-doped fiber laser at 1.3 GHz using a V₂AlC MAX phase nanoparticle-based saturable absorber

We experimentally demonstrate a harmonically mode-locked erbium (Er)-doped fiber laser using a V₂AlC-based saturable absorber (SA) at the 1.55 μm wavelength region. The prepared SA was fabricated using a side-polished fiber with V₂AlC MAXphase nanoparticles via liquid-phase exfoliation (LPE). The derived saturation intensity and modulation depth of the V₂AlC-based SA were approximately 63 MW/cm² and 18%, respectively. The repetition rate was tuned from 14.98 MHz to 1.3 GHz (86th harmonic) by adjusting the pump power. The 86th harmonic mode-locked pulses at approximately 1.3 GHz repetition rate were generated with a temporal width and supermode suppression ratio of approximately 863 fs and 30 dB, respectively. These results demonstrate the application of the V₂AlC MAX phase in giga-hertz frequency ultrafast fiber lasers.