Ultra-long-period grating-based multi-wavelength ultrafast fiber laser [Invited]

We propose and demonstrate the cascaded multi-wavelength mode-locked erbium-doped fiber laser (EDFL) based on ultra-long-period gratings (ULPGs) for the first time, to the best of our knowledge. Study found that the ULPG can be used as both a mode-locker for pulse shaping and a comb filter for multi-wavelength generation simultaneously. Using the dual-function of ULPG, three-, four-, five-, six-, and seven-wavelength mode-locked pulses are obtained in EDFL, seven of which are the largest number of wavelengths up to now. For the four-wavelength soliton pulses, their pulse width is about 7.8 ps. The maximum average output power and slope efficiency of these pulses are 8.4 mW and 2.03%, respectively. Besides the con-ventional pulses, hybrid soliton pulses composed of a four-wavelength pulse and single soliton are also observed. Finally, the effect of cavity dispersion on the multi-wavelength mode-locked pulses is also discussed. Our findings indicate that apart from common sensing and filtering, the ULPG may also possess attractive nonlinear pulse-shaping property for ultrafast photonics application.

Automated summary

This study introduces and demonstrates a cascaded multi-wavelength mode-locked erbium-doped fiber laser based on ULPGs, achieving up to seven wavelengths for the first time. The ULPG serves as both a mode-locker for pulse shaping and a comb filter for multi-wavelength generation simultaneously. The ULPG also exhibits attractive nonlinear pulse-shaping property for ultrafast photonics applications.