Solitons are stable localized wave packets that can propagate long distance in dispersive media without changing their shapes. As particle-like nonlinear localized waves, solitons have been investigated in different physical systems. Owing to potential applications in optical communication and optical signal processing systems, optical solitons have attracted intense interest in the past three decades. To experimentally study the formation and dynamics of temporal optical solitons, fiber lasers are considered as a wonderful nonlinear system. During the last decade, several kinds of theoretically predicted solitons were observed experimentally in fiber lasers. In this review, we present a detailed overview of the experimentally verified optical solitons in fiber lasers, including bright solitons, dark solitons, vector solitons, dissipative solitons, dispersion-managed solitons, polarization domain wall solitons, and so on. An outlook for the development on the solitons in fiber lasers is also provided and discussed.

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Recent progress of study on optical solitons in fiber lasers

Dissipative soliton evolution in passively mode-locked fiber lasers with large net-normal-dispersion and high nonlinearity is investigated numerically and confirmed experimentally. I have proposed a theoretical model including the nonlinear polarization evolution and spectral filtering effect. This model successfully predicts the pulse behaviors of the proposed laser, such as the multi-soliton evolution, quasi-rectangle-spectrum profile, trapezoid-spectrum profile, and unstable state. Numerical results show that, in contrast to the typical net- or all-normal-dispersion fiber lasers with the slight variation of the pulse breathing, the breathing ratios of the pulse duration and spectral width of our laser are more than three and two during the intra-cavity propagation, respectively. The nonlinear polarization rotation mechanism together with spectral filtering effect plays the key roles on the pulse evolution. The experimental observations confirm the theoretical predictions.

Numerical and experimental investigation of dissipative solitons in passively mode-locked fiber lasers with large net-normal-dispersion and high nonlinearity

Generation, optimization, and application of ultrashort femtosecond pulse in mode-locked fiber lasers

We report an $L$ -band passively mode-locked erbium-doped fiber ring laser using the nonlinear polarization rotation technique. The center wavelength of the fiber laser can be tuned from 1575.5 to 1603.6 nm. The 458.7-fs pulses at 1603.6 nm show an 8.6-MHz pulse repetition rate. To the best of our knowledge, it is the longest wavelength for which subpicosecond pulses have been achieved so far with the nonlinear polarization rotation technique.

$L$ -Band Femtosecond Fiber Laser Mode Locked by Nonlinear Polarization Rotation

This paper investigates the zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres (PBGFs) by using a full-vector finite element method. By simulation we found that theoretically the zero dispersion wavelength can be tailored by respectively changing the rounded diameter of air holes, pitch, refractive index, normalized thickness of core rings, and hole diameter to pitch ratio. At the same time the tailoring of dispersion slope can also be realized by changing the rounded diameter of air holes or pitch or normalized thickness of core rings. To illustrate the reasonability of fibre designs, this paper also gives the variance of normalized interface field intensity which measures the scattering loss relatively versus wavelength for different designs. From the viewpoint of loss, varying the rounded diameter and the thickness of core ring could shift zero wavelength but it is difficult to get the required parameters within so tiny range in practical drawing of PBGFs, on the other hand, it is possible in practice to respectively alter the pitch and refractive index to shift zero wavelength. But varying hole diameter to pitch ratio is not worthwhile because they each induce large increase of loss and narrowness of transmission bandwidth. The zero dispersion wavelength can be engineered by respectively varying the rounded diameter of air holes, pitch, refractive index, and normalized thickness of core rings without incurring large loss penalties.

Zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres

Approaching 100 nJ pulse energy output from a mode-locked photonic crystal fiber laser

An ytterbium-doped single polarization large-mode-area photonic crystal fiber laser amplifier is demonstrated, which can deliver average power of 16 W at a repetition rate of 50 MHz, corresponding to 320 nJ pulse energy. The length of the fiber is 3.5 m, and the pulse could be shorter since the spectrum is further broadened due to the SPM. The pulse duration is compressed to 85 fs after passing through a grating pair. The oscillator and amplifier of the system are composed of the same single polarization large-mode-area photonic crystal fiber, resulting in better environmental stability and compactness.

Hu Ming-Lie

Papers

Approaching 100 nJ pulse energy output from a mode-locked photonic crystal fiber laser

Sub-100 fs high power Yb-doped single polarization large-mode-area photonic crystal fiber laser amplifier

A high power photonic crystal fiber laser oscillator based on nonlinear polarization rotation mode-locking

A Long-Cavity All-Normal-Dispersion Mode-Locked Yb-Doped Fiber Laser

Hundreds of Megawatts Peak Power Multi-Core Photonic Crystal Fiber Laser Amplifier