Towards visible-wavelength passively mode-locked lasers in all-fibre format

Mode-locked fibre lasers generating ultrashort pulses with the advantages of robustness, compactness and excellent beam quality are of tremendous interest in applications such as laser material processing, medicine, precision measurement, biological photonics, ultrafast spectroscopy, optical communication and scientific research. In recent decades, mode-locked ultrafast fibre lasers operating in the near-infrared and mid-infrared spectral regions have been well developed, but ultrafast laser sou...