Generation of 1 nJ pulses directly from passively mode-locked Er3+-doped ring fiber laser without dispersion compensation

A novel method for generation of high-energy femtosecond pulses from passively mode-locked Er³⁺-doped fiber laser is presented by combining lumped amplification and high coupling output. The numerical and experimental results show that the method can effectively lower the periodic perturbation, avoid multiple pulse lasing, and permit high-energy ultra-short pulses to be formed. Based on nonlinear polarization evolution technique, the stable mode-locked pulses with energies of more than 1 nJ for 205 fs at a 14.2 MHz repetition rate have been successfully obtained. To our knowledge, it is the highest single-pulse energy obtained to date directly from Er³⁺-doped fiber lasers without using dispersion compensation technique. The lasing wavelength is centered at 1560 nm with 3 dB bandwidth of about 18 nm and the average output power is 14.6 mW.