Compact all-fiber high-energy fiber laser with sub-300-fs duration

Generation of high-energy rectangular pulses in a nonlinear polarization rotation mode-locked ring fiber laser

In this paper, a novel high-energy mode-locked fiber laser based on the nonlinear polarization rotation (NPR) technique is presented to generate 331 nJ rectangular pulses. When pump power was 2659 mW, the maximum output power would be 102.3 mW; the maximum peak power was 41.74 W under the pump power of 1766 mW. In this study, the use of two homemade laser diodes and other common fiber devices was a vital step to achieve the low-cost and high-efficiency NPR mode-locked fiber laser. Based on these results, a novel approach could be developed to realize a high-energy rectangular pulse and promote the practical applications of the NPR mode-locked fiber laser in the field of ultrafast photonics.

Conventional soliton or stretched pulse delivered by nanotube-mode-locked fiber laser

We propose a nanotube-mode-locked erbium-doped fiber laser that can deliver conventional solitons (CSs) or stretched pulses (SPs) based on a D-shaped fiber saturable absorber where evanescent-field interaction works. The net cavity dispersion of the laser is slightly negative. In our experiment, by optimizing the polarization controller in the cavity, CS and SP can be obtained at the central wavelengths of 1530.6 nm and 1530.3 nm due to carbon nanotubes and the spectral filtering effect induced by nonlinear polarization rotation. Although the acquired CS and SP nearly have the same central wavelengths, they show distinct optical spectra, 3-dB bandwidths. The proposed fiber laser is attractive for practical applications.

80 nJ ultrafast dissipative soliton generation in dumbbell-shaped mode-locked fiber laser

A novel all-fiberized dumbbell-shaped mode-locked fiber laser was developed to directly generate 80 nJ dissipative solitons, which can be linearly compressed from 85 to 1.2 ps externally with a diffraction grating pair. The pulse peak power reached 42 kW after compression. With the most available pump power, stable dissipative soliton bundles with up to 628 nJ bundle energy were obtained. The corresponding average output power reached 2.2 W. The employment of dual-nonlinear-optical-loop mirrors and large-mode-area fibers in the cavity played an essential role in improving structural compactness and producing high-energy ultrafast pulses. To the best of our knowledge, these are the most energetic compressible dissipative solitons generated from a strictly all-fiber cavity.

MoS2-clad microfibre laser delivering conventional, dispersion-managed and dissipative solitons

Molybdenum disulfide (MoS₂), whose monolayer possesses a direct band gap, displays promising applications in optoelectronics, photonics, and lasers. Recent researches have demonstrated that MoS₂ has not only a significant broadband saturable absorption performance, but also a higher optical nonlinear response than graphene. However, MoS₂ shows much lower optical damage threshold owing to the poorer thermal conductivity and mechanical property. Here, we exploit a MoS₂-clad microfibre (MCM) as the saturable absorber (SA) for the generation of ultrashort pulses under different dispersion conditions. The improved evanescent field interaction scheme can overcome the laser-induced thermal damage, as well as take full advantage of the strong nonlinear effect of MoS₂. With the MCM SA, conventional, dispersion-managed, and dissipative solitons are generated around 1600 nm in Er-doped fibre lasers with anomalous, near-zero, and normal cavity dispersions, respectively. Our work paves the way for applications of 2D layered materials in photonics, especially in laser sources.

Flexible pulse-controlled fiber laser

Controlled flexible pulses have widespread applications in the fields of fiber telecommunication, optical sensing, metrology, and microscopy. Here, we report a compact pulse-controlled all-fiber laser by exploiting an intracavity fiber Bragg grating (FBG) system as a flexible filter. The width and wavelength of pulses can be tuned independently by vertically and horizontally translating a cantilever beam, respectively. The pulse width of the laser can be tuned flexibly and accurately from ~7 to ~150 ps by controlling the bandwidth of FBG. The wavelength of pulse can be tuned precisely with the range of >20 nm. The flexible laser is precisely controlled and insensitive to environmental perturbations. This fiber-based laser is a simple, stable, and low-cost source for various applications where the width-tunable and/or wavelength-tunable pulses are necessary.

Experimental and theoretical investigations of a tunable dissipative soliton fiber laser

A tunable dissipative soliton fiber laser based on carbon nanotubes and the nonlinear polarization rotation (NPR) technique has been investigated experimentally and numerically for the first time to the author's best knowledge. The laser proposed delivers strongly chirped solitons with pulse duration of ∼220  ps and a spectral width of ∼5.6  nm. With the NPR-related filtering effect, the output pulses are wavelength tunable over the range from 1566 to 1593 nm by adjusting the polarization controller (PC). Numerical results are in good agreement with experimental observations and clearly reveal that the tunable mode-locking operation is attributed to the variation of phase delay caused by the PCs.

Vector rectangular-shape laser based on reduced graphene oxide interacting with a long fiber taper

A vector dual-wavelength rectangular-shape laser (RSL) based on a long fiber taper deposited with reduced graphene oxide is proposed, where nonlinearity is enhanced due to a large evanescent-field-interacting length and strong field confinement of an 8 mm fiber taper with a waist diameter of 4 μm. Graphene flakes are deposited uniformly on the taper waist with light pressure effect, so this structure guarantees both excellent saturable absorption and high nonlinearity. The RSL with a repetition rate of 7.9 MHz shows fast polarization switching in two orthogonal polarization directions, and temporal and spectral characteristics are investigated.

Observation of vector- and scalar-pulse in a nanotube-mode-locked fiber laser

We report the experimental observations of vector pulse trapping and scalar dissipative soliton in a compact nanotube-mode-locked all-fiber laser for the first time to our best knowledge. The vector pulse exhibits a smooth Gaussian spectral profile without any sidebands. Although two orthogonally polarized components of the vector pulse have different central wavelengths, they copropagate as a unit in the laser cavity with the same speed. The scalar dissipative soliton shows a rectangular spectrum with pulse duration of ~13 ps, and can be compressed to ~320 fs external to the cavity. This flexible laser provides stable, ultrashort vector- and scalar-pulsed sources, which is convenient and attractive for practical applications.

Compact all-fiber laser delivering conventional and dissipative solitons

We report the simultaneous generation of conventional soliton (CS) and dissipative soliton (DS) in a mode-locked fiber laser exploiting chirped fiber Bragg grating and four-port circulator. The bandwidth and duration of the CS are 0.28 nm and 15.1 ps, respectively. However, the giant-chirp DS exhibits a quasi-rectangular spectrum with a bandwidth of 9.5 nm. The duration of the output DS is 7.3 ps and can be compressed to 0.55 ps external to the cavity. Our numerical results agree well with the experimental observations. The flexible all-fiber laser can provide three different pulse sources, which is convenient and attractive for practical applications.

Graphene and nanotube mode-locked fiber laser emitting dissipative and conventional solitons

We propose a bidirectional erbium-doped fiber laser mode-locked with a mixture of graphene and single-walled carbon nanotubes for the first time to our best knowledge. The fiber laser can deliver dissipative soliton (DS) and conventional soliton (CS), circulating in opposite directions. The net-cavity dispersion is normal in the clockwise direction and anomalous in counter clockwise direction, respectively, and then DS and CS are generated with the suitable adjustment of attenuators. The output DS and CS approximately have the same central wavelength, but exhibit different optical spectra, pulse durations, and repetition rates. The all-fiber switchable laser can provide two different pulse sources, which is convenient for practical applications.

Bidirectional fiber soliton laser mode-locked by single-wall carbon nanotubes

We report on the experimental observation of a bidirectional fiber soliton laser passively mode-locked by single-wall carbon nanotubes. Two stable pulse trains in opposite directions are delivered simultaneously from the ring cavity. The counterpropagating pulses have different central wavelengths, pulse durations, and repetition rates. By adjusting the fiber birefringence and cavity length, the central wavelengths of two solitons can be the same or different. Experimental observations and analyses demonstrate that the different operating wavelengths result in the unequal repetition rates of two pulses. These unique features may be attributed to the cavity asymmetry and fiber birefringence.

Coexistence of unequal pulses in a normal dispersion fiber laser

We experimentally demonstrate unequal pulses delivered from an erbium-doped fiber (EDF) laser with net-normal dispersion. Two types of pulses with different durations, energies, and spectra coexist in the same ring cavity. The output spectrum exhibits a broadband base that corresponds to the main pulse and a small rectangular lump that corresponds to the additional satellite pulse. With the enhancement of pump power, the intensity of main pulse almost keeps unchanged while the satellite pulse nearly increases linearly. Based on experimental results, it is indicated that two different pulse shaping mechanisms coexist in laser cavity, where the nonlinear polarization rotation (NPR) and spectral filtering (SF) effect contribute to the formation of main pulse and satellite pulse, respectively.

Generation and amplification of high-energy nanosecond pulses in a compact all-fiber laser

We have experimentally investigated high-energy rectangular pulses delivering from an erbium-doped fiber laser operating in ultra-large net-negative-dispersion regime. The laser oscillator emits rectangular pulses with approximately Gaussian spectral profiles, adjustable nanoseconds durations, and multi-ten nanojoule energies. The outputted pulses can be further amplified to over 2 μJ without distortion by a two-stage erbium-doped fiber amplifier. Thus, rectangular pulses with controllable durations and energies can be achieved from the compact all-fiber fiber laser system.

Experimental investigation of square dissipative soliton generation and propagation

We have experimentally investigated the generation and propagation of square dissipative solitons emitted from an erbium-doped fiber laser with large normal cavity dispersion. The square pulse exhibits an approximately Gaussian spectral profile and large frequency chirp on its edges. When the square pulse propagates through a segment of single-mode fiber (SMF), it can be shaped to a Gaussian pulse and the corresponding spectrum will have a redshift with a prolonged wing on the longer wavelength. Our experiments show that the pulse evolution in the SMF is determined by the combined effects of the fiber dispersion, intrapulse Raman scattering, and the pulse initial chirps.