Impact of spectral filtering on pulse breaking-up and noise-like pulse generation in all-normal dispersion fiber lasers.

Based on mathematic simulations, the impact of spectral filtering on pulse breaking up and noise-like pulse generation in all-normal-dispersion fiber lasers are investigated. Three types of spectrum filters are employed in the simulations, which have a Gaussian-shaped profile, super-Gaussian-shaped profile, and sinusoidal-shaped profile, respectively. With the Gaussian-shaped filter, the pulse breaking-up process is discussed. The super-Gaussian-shaped filter and the sinusoidal-shaped filter have two different formation mechanisms for noise-like pulses and are revealed. In addition, with the sinusoidal-shaped filter, dissipative solitons of different central wavelengths are achieved.

Generation of noise-like pulses with a 920 fs pedestal in a nonlinear Yb-doped fiber amplifier.

We demonstrate the compression of noise-like pulses in an Yb-doped fiber master-oscillator power-amplifier (MOPA). The seed source of the MOPA is an NPR mode locked fiber laser delivering 5.94-ps dissipative soliton pulses with a repetition rate of 37.48 MHz. After amplification in the Yb-doped fiber amplifier, stable noise-like pulses with maximum power of 5 W are obtained. Subsequently a grating pair is used to tailor the spectrum and compensate the dispersion of the amplified noise-like pulses. The pedestal of de-convolution autocorrelation trace is compressed from 6.5 ps to 920 fs. To the best of our knowledge, this is the first time that the pedestal of a noise-like pulse is compressed to femtosecond region.

Noise-like pulses with a 14.5 fs spike generated in an Yb-doped fiber nonlinear amplifier.

We demonstrate noise-like pulses with a 14.5 fs spike generated in an Yb-doped fiber nonlinear amplifier after compression, while the pedestal has a width of 3.70 ps. This Yb-doped fiber nonlinear amplifier is seeded by dissipative solitons. With an average output power of 5 W, the single pulse energy is approximately 200 nJ at a repetition rate of 24.65 MHz. Mathematical research based on the coupled nonlinear Schrödinger equations about the generation and the compressibility of the noise-like pulses is also carried out.

Compact Yb-doped mode-locked fiber laser with only one polarized beam splitter.

We experimentally demonstrate a kind of simplified Yb-doped mode-locked fiber laser with a nonlinear polarization rotation technique. In the oscillator, there are no waveplates, physical bandpass filters, or polarization controlling devices except for one polarized beam splitter and a polarization-independent isolator. In the experiment, self-started stable mode locking pulse trains are obtained with four different cavity lengths: 110 m, 66 m, 50 m, and 26 m. To make clear the mechanism of pulse formation of this kind of simplified fiber laser, the characteristics of which are called an artificial saturable absorber, are discussed and the influences of these parameters on mode locking are also analyzed.