We demonstrated the formation of noise-like square-wave pulses in an Er-doped fiber laser, using a microfiber based topological insulator as a saturated absorber (SA). The SA guaranteed both excellent saturable absorption and high nonlinearity. The pulse width can be increased ranging from 0.985 to 5.503 ns by increasing the pump power from 212 to 284 mW with the polarization state fixed. Moreover, with the adjustment of the polarization controllers in the cavity, the pulse width can be adjusted obviously. Worth mentioning, it was the first time that the noise-like square-wave pulse formed in a microfiber based topological insulator fiber laser.
We experimentally investigated the polarization vector characteristics in an Er-doped fiber laser based on graphene that was deposited on microfiber. A variety of dynamic states, including polarization locked fundamental soliton, and polarization domain wall square pulses and their harmonic mode locked counterparts have all been observed with different pump powers and polarization states. These results indicated that the microfiber-based graphene not only could act as a saturable absorber but also could provide high nonlinearity, which is favorable for the cross coupling between the two orthogonal polarization components. It was worth to mention that it is the first time to obtain the polarization domain wall solitons in a mode locked fiber laser.
We experimentally generated the duration-controllable square-wave pulse from an L band dissipative soliton (DS) fiber laser based on the dispersive Fourier transformation (DFT) technique. The rectangular spectrum emitted from an L band dissipative soliton fiber laser is mapped into a time-domain coherent rectangular waveform through the DFT technique. The duration of the square-wave pulse can be controllable with the adjustments of the pump power. The results demonstrate that it is an effective and flexible way to achieve duration-controllable square-wave pulses by combinating with DFT technique and DS fiber laser.
We have experimentally investigated supercontinuum generated by using different pulse dynamics patterns as the
pump pulses. These patterns, which include conventional mode-locked single pulse, condensed phase pulses and
pulsed bunches, were all directly produced from a mode-locked erbium-doped fiber laser based on a multi-layer
graphene saturable absorber. The strong third-order optical nonlinearity of graphene and all fiber cavity
configuration led to the multi-pulses operation states at a low pump power. A flat supercontinuum with 20-dB width
of 550 nm from 1200 nm to 1750 nm have all been obtained by seeding the amplified conventional mode-locked
single pulse and condensed phase pulses into a segment of photonic crystal fiber. On the other hand, experimental
results also show that the pulsed bunches was not conducive to form a flat supercontinuum.
We have experimentally observed bright-dark soliton pairs in an erbium-doped fiber ring laser for the first time. This approach is different from the vector dark domain wall solitons which separate the two orthogonal linear polarization eigenstates of the laser emission. In our laser, the bright-dark soliton pairs can co-exist in any one polarization state. Numerical simulations based on the coupled complex Ginzburg-Landau equations have confirmed the experimental results.
Bright-dark soliton pairs and bright or dark solitons have all been observed by adjusting the triggering level of a digital
oscilloscope in a self-mode locking erbium-doped fiber ring laser.
We have proposed and demonstrated a passively harmonic mode-locked fiber laser based on a single-walled carbon
nanotube saturable absorber (SWCNT-SA) that has a controllable repetition rate. With the pump power fixed, we have
experimentally observed harmonically mode-locked optical pulses with repetition rates that can be controlled over the
range from the fundamental to the seventh-order mode through careful adjustment of the polarization controller only.
From the experimental results, we deduce that the likely origin of the self-stabilization is the result of global and local
soliton interactions induced by the continuous wave (CW) components.
The generation of high energy, wavelength-tuned supercontinuum sources has been investigated numerically. A stable wavelength-tunable soliton source was first obtained by compressing a pulse with a parabolic shape in a dispersion decreasing fiber. Subsequently, a widely tunable supercontinuum was generated by propagating the resulting soliton in a highly nonlinear silica fiber. In this paper, we have also investigated the influence of the width, the initial chirps, and the pulse shape of the compressed pulse on the generation of the supercontinuum.
We have theoretically studied pulse propagation in a normal-dispersion optical cubicon fiber amplifier (NDOCFA) with
an arbitrary longitudinal gain proflie, and have obtained an analytic solution for the nonlinear Schrödinger equation that
describles such an amplifier. The results show that the characteristics of self-similarity and linear chirp will be lost due to
third-order dispersion. However, by using a dispersion compensation technique, one can obtain efficient and high-quality
compressed pulses. The numerical simulation is consistent with the analytic results.
Compression of chirped free femtosecond pulses in hollow core photonic bandgap fibers is investigated numerically. The
results show that intrapulse stimulated Raman scattering can improve the quality of the compressed pulse. Positive
third-order dispersion is the main limitation on the compression of the femtosecond pulse. However, the combined effect
of the intrapulse stimulated Raman scattering and the negative third-order dispersion can form still shorter pulses than is
possible with intrapulse stimulated Raman scattering alone. We also investigate the influence of width and peak power
of input pulse on pulse compression.
Using the nonlinear polarization rotation technique and an Er3+/Yb3+ co-doped fiber amplifier, we have
experimentally obtained high output power wavelength continuously tunable laser and high output power passively
mode-locked pulse in an erbium-doped fiber ring laser.
The onset of supercontinuum generation in a photonic crystal fiber (PCF) is investigated experimentally and numerically as a function of pump optical power with a femtosecond pulse. The pump pulse wavelength is positioned in the normal-dispersion regime close to the zero-dispersion wavelength (ZDW) of the PCF. When the pump power is low, the self phase modulation (SPM) is the dominant nonlinear process. With the increasing pump power, the primary mechanism of spectral broadening is identified as the combined action of stimulated Raman scattering (SRS) and parametric four-wave mixing (FWM). In the experiment, we have also observed the anti-Stokes Raman component, which reveals the importance of the fact that the pump pulses are positioned near the ZDW. Third-order dispersion (TOD) and Raman self frequency shift (RSS) also contribute to the supercontinuum generation. Good agreement between experiment and simulation is obtained.
By using the nonlinear polarization rotation (NPR), we demonstrated a novel wavelength-tunable narrow linewidth
erbium-doped fiber ring laser (EDFL) with a maximum tuning rang up to 25 nm (from 1532.0 nm to 1557.2 nm). The
NPR effect effectively induced intensity- and wavelength-dependent loss to alleviate mode competition caused by
homogenous gain broadening in erbium-doped fibers. By adjusting the polarization controllers in the cavity, the laser has
a power-equalized output, and the output power fluctuation between different wavelengths is smaller than 0.2dB, the
line-width of each light laser is 0.06 nm by 3 dB.
The onset of supercontinuum generation in a photonics crystal fiber is investigated experimentally and numerically as
a function of pump optical power with a femtosecond pulse. The effects of optical wave breaking of higher-order solitons,
Stimulated Raman scattering (SRS), and coupling between the SRS and parametric four-wave mixing on supercontinuum
generation are investigated. Good agreement between experiment and simulation is obtained.
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