Generation and amplification of the ultrashort optical pulses in passive harmonic mode-locking Er3+-doped fiber laser

The experimental results of the stable high-order harmonic mode-locking pulses generation and amplification in Er3+-doped fiber amplifiers is reported. Using nonlinear polarization rotation (NPR) effect, the artifical saturable absorber is generated and the stable high-order harmonic mode-locking pulses have been generated from Er3+-doped ring fiber laser (407.6 MHz repetition rate harmonic mode-locking has been obtained due to the limited bandwidth of the osciloscope). Three different ways have been found, through which high-order harmonic mode-locking pulses have been generated. The stable 4th harmonic mode-locking (83.52 MHz) pulses have been generated accompanying with soliton side-band in the output spectra of the pulses. After the high concentration Er3+-doped fiber amplification (6 m in length, 2700 ppm), the 4th harmonic mode-locking pulses (83.52 MHz) are amplified to an average power of 13.88 mW. The amplified pulses is of a pulse width 201 fs, with central wavelength of 1.531 μm, single pulse energy of 0.166 nJ corresponding to 0.811 × 103 W peak power, a gain of 19 dB with 83.52 MHz repetition rate.