Mode-locked Soliton Fiber Laser Research Articles

Soliton and bound-state soliton mode-locked fiber laser based on a MoS2/fluorine mica Langmuir–Blodgett film saturable absorber

In this article, we report on an experimentally generated soliton and bound-state soliton passively mode-locked erbium-doped fiber laser by incorporating a saturable absorber (SA) made of MoS2/fluorine mica (FM) that was fabricated with the Langmuir–Blodgett (LB) method. The FM substrate is 20 μm thick and easy to bend or cut, like a polymer. However, it has a higher damage threshold and a better thermal dissipation than polymers. In addition, the LB method can be used to fabricate a thin film with good uniformity. In this study, the modulation depth, saturable intensity, and unsaturated loss of the SA are measured as 5.9%, 57.69 MW/cm2, and 13.4%, respectively. Based on the SA, a soliton mode-locked laser is achieved. The pulse duration, repetition rate, and signal-to-noise ratio are 581 fs, 15.67 MHz, and 65 dB, respectively. By adjusting the polarization controller and pump power, we obtain a bound-state soliton mode-locked pulse. The temporal interval between the two solitons forming the bound-state pulse is 2.7 ps. The repetition rate of the bound-state pulses is proportional to the pump power. The maximum repetition rate is 517 MHz, corresponding to the 33rd harmonic of the fundamental repetition rate. The results indicate that the MoS2/FM LB film absorber is a promising photonic device in ultrafast fiber lasers.

Soliton mode-locked fiber laser with high-quality MBE-grown Bi2Se3 film

In this work, a soliton mode-locked erbium-doped fiber laser (EDFL) with a high-quality molecular beam epitaxy (MBE)-grown topological insulator (TI) Bi2Se3 saturable absorber (SA) is reported. To fabricate the SA device, a 16-layer Bi2Se3 film was grown successfully on a 100 μm thick SiO2 substrate and sandwiched directly between two fiber ferrules. The TI-SA had a saturable absorption of 1.12% and a saturable influence of 160 MW/cm2. After inserting the TI-SA into the unidirectional ring-cavity EDFL, self-starting mode-locked soliton pulse trains were obtained at a fundamental repetition rate of 19.352 MHz. The output central wavelength, pulse energy, pulse duration, and signal to noise ratio of the radio frequency spectrum were 1530 nm,18.5 pJ, 1.08 ps, and 60 dBm, respectively. These results demonstrate that the MBE technique could provide a controllable and repeatable method for the fabrication of identical high-quality TI-SAs, which is critically important for ultra-fast pulse generation.

L-Band Efficient Dissipative Soliton Erbium-Doped Fiber Laser With a Pulse Energy of 6.15 nJ and 3 dB Bandwidth of 47.8 nm

Here, an efficient dissipative soliton mode-locked fiber laser in the L-band using nonlinear polarization rotation technology is demonstrated. With a maximum pump power of 495.3 mW and polarization state optimization, the fiber laser delivers a maximum output power of 68.6 mW with an 11.16 MHz repetition rate and corresponding single pulse energy of 6.15 nJ. The dissipative soliton spectrum is centered at 1599.6 nm with a 3 dB bandwidth of 47.8 nm. The full width at half maximum of the compressed pulse is 156 fs. To the best of our knowledge, this is the highest single pulse energy reported so far for an L-band passively mode-locked all-fiber laser.

Ultrafast soliton and stretched-pulse switchable mode-locked fiber laser with hybrid structure of multimode fiber based saturable absorber

We demonstrate an all-fiber mode locked laser based on hybrid structure of multimode fiber saturable absorber (SA) that can realize both conventional soliton and stretched-pulse states. Stable 16.44 MHz conventional soliton pulses are achieved by injecting 80 mW threshold pump power. By increasing the incident pump power to 420 mW, the laser evolves from soliton operation into stretched-pulse mode locking state. 310 fs stretched-pulse are obtained with the same repetition rate as the soliton pulses. The center wavelength and its 3 dB spectrum bandwidth are 1603 nm and 14.2 nm, respectively. For the first time, we experimentally confirm transition between conventional soliton and stretched-pulse in 1.5 μm mode-locked fiber laser by introducing multimode optical fiber SA. Moreover, the maximum single pulse energy of nearly 1 nJ is achieved. Such all-fiber mode-locked lasers based on hybrid structure of multimode fiber are attractive for practical applications without damage and the limitation of life time.

High-energy dissipative soliton-driven fiber optical parametric oscillator emitting at 1.7 µm

We report a fiber optical parametric oscillator (FOPO) synchronously pumped in a C-band, delivering high-energy picosecond pulses exceeding the nanojoule level of around 1700 nm. The gain medium is a dispersion-shifted fiber, pumped by highly-chirped pulses from a mode-locked dissipative soliton fiber laser. Optimizing the pump wavelength along with time-dispersion-tuning of the FOPO enabled a broad tunability from 1617–1876 nm for the idler wave. In addition, relative intensity noise levels below −140 dBc Hz−1 have been achieved, paving the way for using such a source in biophotonics and instrumentation.

Relative Intensity Noise of Hybrid Mode-Locked Bound Soliton Fiber Laser: Theory and Experiment

Relative intensity noises (RIN) of mode-locked lasers are properties which are crucial for applications. In the literature, there have been plenty of theoretical/experimental studies on the RIN noises of passive/active single-pulse mode-locked lasers. Since some mode-locked lasers can also be operated under the bound-pulse mode-locking state, it is thus very interesting to further examine the RIN properties under bound-pulse mode-locking, and to verify if there are possibilities for RIN noise reduction as predicted by some previous theoretical works. The conventional analytical formula based on the soliton perturbation theory can no longer be applied due to the pulse shape complexity for the bound-pulse mode-locking cases. New theoretical tools for modelling general mode-locked lasers are eagerly awaited. In the present work, the RIN noises of an environmentally stable 10 GHz hybrid mode-locked Er-doped fiber laser capable of bound-soliton generation are experimentally investigated, and a novel theoretical method based on the linearized backpropagation approach is theoretically developed for calculating the RIN noise spectra of general mode-locked lasers. Both the theoretical and experimental results demonstrate that the RIN noise of the bound-soliton state can be lower than that of the single-soliton state by following the laser power scaling tendency.

Sub-200 fs soliton mode-locked fiber laser based on bismuthene saturable absorber

Few-layer bismuthene is an emerging two-dimensional material in the fields of physics, chemistry, and material science. However, its nonlinear optical property and the related photonics device have been seldom studied so far. Here, we demonstrate a sub-200 fs soliton mode-locked erbium-doped fiber laser (EDFL) using a microfiber-based bismuthene saturable absorber for the first time, to the best of our knowledge. The bismuthene nanosheets are synthesized by the sonochemical exfoliation method and transferred onto the taper region of a microfiber by the optical deposition method. Stable soliton pulses centered at 1561 nm with the shortest pulse duration of about 193 fs were obtained. Our findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.

Soliton mode-locked thulium-doped fiber laser with cobalt oxide saturable absorber

Abstract In this work, we propose and demonstrate a mode-locked thulium doped fiber laser (TDFL) with an integrated cobalt oxide (Co3O4) saturable absorber (SA). The SA is fabricated by suspending Co3O4 nanosheets in a polymer film before being secured between two fiber ferules. The laser operates in the anomalous dispersion regime, confirmed by the Kelly sidebands observed in the obtained optical spectrum. Mode-locking operation is obtained at a low threshold pump power of 77.32 mW, with further optimizations made using a polarization controller The laser generates pulses with a repetition rate of 11.36 MHz and a pulse width of 1.39 ps. The generated pulses are highly stable, with a high signal-to-noise ratio of 46.00 dB and minimum power fluctuations indicating a long-term stability. This work demonstrates a simple and a low-cost laser that would have potential applications for operation near the 2.0-µm region, especially for medical applications.

Ultrashort pulse generation with an erbium-doped fiber laser ring cavity based on a copper oxide saturable absorber.

A soliton mode-locked erbium-doped fiber (EDF) laser has been experimentally demonstrated using copper oxide (CuO) thin film as a saturable absorber (SA). The dispersion of the EDF cavity including the CuO-SA was balanced by a suitable length of single-mode fiber (SMF). The fabricated CuO-SA has 3.5% modulation depth and 3.3 MW/cm2 saturation intensity. The mode-locked train pulses have 1.7ps pulse width and 983kHz repetition rate, while the pulse energy and output power are 1.29nJ and 1.27mW, respectively, at maximum pump power of 159mW. These results indicate that the CuO thin film is a good SA candidate for a fiber laser operating at a low pump power. To the best of our knowledge, this is the first demonstration of a CuO-SA-based mode-locked fiber laser.

Dynamics of Dispersive Wave and Regimes of Different Kinds of Sideband Generation in Mode-Locked Soliton Fiber Lasers

We give a thoroughly theoretical and numerical investigation of sidebands generation in mode-locked soliton fiber lasers for the first time. A simple and reliable numerical method is proposed to separate the dispersive wave and soliton in the ultrashort pulse of a mode-locked fiber laser. We find that the dip-type sideband generation can be regarded as a locally destructive interference between the resonance-enhanced dispersive waves and solitons, which can also be explained by the parametric process in the fiber laser. The dip-type sidebands are also Kelly sidebands according to their formation. Simulations confirm the rationality of our proposed explanation and method. Our work gives an insight into the dynamics of soliton mode-locked fiber lasers.

Polarization Rotation Dynamics in Harmonically Mode-Locked Vector Soliton Fiber Lasers

Polarization rotation dynamics for group velocity locked vector solitons in higher order harmonically mode-locked soliton fiber lasers are studied for the first time, in a thulium/holmium fiber laser. In a linear ultrafast fiber laser with net anomalous dispersion, harmonically mode-locked states are generated continuously by increasing the pump power for specific net cavity birefringence settings. The polarization evolution frequency remains the same for all harmonically mode-locked pulse trains, converging toward a singular solution close to the maximum pulse intensity modulation depth for each respective harmonically mode-locked state. With a polarization resolved output, an intensity modulation of the ultrafast pulse train with varying pulse binning is recorded, corresponding to the polarization rotation of the vector solitons. In addition, a polarization rotation vector soliton state with two different sets of RF sidebands symmetric to the repetition rate is observed, which leads to a more complex modulated pulse train. The experimental results of the polarization evolution also matche well with the presented theoretical modeling. Similar relative intensity noise <0.4% for all harmonically mode-locked states is measured. This method to modulate the intensity of an ultrafast pulse train and tune its pulse spacing by integer fractions of the initial round trip time shows a strong potential for applications in optical communications, polarization de multiplexing schemes, and sensing.

Sub-200 femtosecond dispersion-managed soliton ytterbium-doped fiber laser based on carbon nanotubes saturable absorber.

Ultrafast fiber laser light sources attract enormous interest due to the booming applications they are enabling, including long-distance communication, optical metrology, detecting technology of infra-biophotons, and novel material processing. In this paper, we demonstrate 175 fs dispersion-managed soliton (DMS) mode-locked ytterbium-doped fiber (YDF) laser based on single-walled carbon nanotubes (SWCNTs) saturable absorber (SA). The output DMSs have been achieved with repetition rate of 21.2 MHz, center wavelength of 1025.5 nm, and a spectral width of 32.7 nm. The operation directly pulse duration of 300 fs for generated pulse is the reported shortest pulse width for broadband SA based YDF lasers. By using an external grating-based compressor, the pulse duration could be compressed down to 175 fs. To the best of our knowledge, it is the shortest pulse duration obtained directly from YDF laser based on broadband SAs. In this paper, SWCNTs-SA has been utilized as the key optical component (mode locker) and the grating pair providing negative dispersion acts as the dispersion controller.

Generation of two-soliton and three-soliton molecules in a circular fiber array laser

In this work, the generation of two-soliton and three-soliton molecules in a circular fiber array laser with an active optical central fiber is studied. Certain fibers of the array are excited by Gaussian and super-Gaussian pulses. The central fiber of the circular fiber laser is a rare-earth doped fiber. A circular fiber array is employed as a saturable absorber in a soliton mode locked fiber laser. Generation of two-soliton and three-soliton molecules are observed in our simulation. Numerical calculation of binding energy shows that the super-Gaussian pulse tends to be more stable, and therefore it would be a proper choice for the generation of soliton molecules in the circular fiber array laser.

Tunable SESAM-Based Mode-Locked Soliton Fiber Laser in Linear Cavity by Axial-Strain Applied to an FBG

A self-started stable tunable mode-locked soliton fiber laser in a linear cavity structure composed by commercial passive elements is presented in this paper. It is based on the combination of an erbium-doped fiber as the active medium, and a saturated fiber Bragg grating (FBG) as a partial mirror of the cavity. The other side of the cavity consists of a semiconductor saturable absorber mirror acting also as the mode-locking device. The central wavelength of the FBG is selected by the application of axial strain giving rise to a tunable soliton over 8.6 nm on the C band with a variable spacing of 0.01 nm. The laser delivers 18.9 ps long pulses with a 0.14 nm bandwidth, an 8.2 MHz repetition rate, a pulse energy of 89 pJ, and a peak power of 4.71 W.

Subsideband Generation Associated with Period-N Pulsations in Tm Soliton Fiber Lasers

In mode-locked thulium soliton fiber lasers, we experimentally observe and numerically confirm the formation of numerous dispersive-wave sidebands, following a bifurcation of the pulse dynamics into a stationary short-period pulsation. These resonant sidebands appear in addition to the Gordon-Kelly sidebands that are formed in the stationary mode-locked regime. The origin of these sidebands is discussed, highlighting their complexity that does not comply with a simple modulation instability analysis.

Self-starting dropout-free harmonic mode-locked soliton fiber laser with a low timing jitter.

We demonstrate a simple, but robust, self-starting environmentally stable passive harmonic mode-locked femtosecond Er-fiber laser with a scalable repetition rate of up to the 10th harmonic and >50 dB of supermode suppression. The repetition rate of short- and long-term operation for each harmonic appears to have no pulse dropout. Furthermore, at as low as 0.8 and 2.1mHz standard deviation, the repetition rate is achieved by using the pump-induced nonlinearity to modulate the refractive index of the gain fiber.

Ultrafast soliton mode-locked Zirconia-based Erbium-doped fiber laser with carbon nanotubes saturable absorber

Ultrafast soliton mode-locked fiber laser was successfully generated in zirconia-yttria-alumina (Zr-Y-Al) co-doped erbium-doped fiber laser cavity using a single-wall carbon nanotubes (SWCNTs) as saturable absorber. The laser cavity was 11.5 m long with the group delay dispersion of -0.04 ps2. The laser generates soliton pulse train with a center wavelength and 3 dB bandwidth of 1564.2 nm and 3.8 nm, respectively at pump power of 92 mW. Meanwhile, the repetition rate, pulse duration and pulse energy were 17.7 MHz, 770 fs and 51.4 nJ.

An All-Fiber Supercontinuum Source With 30.6-W High-Power and Ultrawide Spectrum Ranging From 385 nm to Beyond 2400 nm

An all-fiber high power, blue-enhanced supercontinuum generation in a piece of uniform photonic crystal fiber pumped by a picosecond Yb-doped master oscillator power amplifier (MOPA) is experimentally demonstrated. The MOPA source is seeded by an actively dissipative soliton mode-locked Yb-doped fiber laser with a fundamental repetition rate of approximately 15.33 MHz and a large chirp. By introducing giant chirp to the seed pulses and optimizing the pump power in every stage of the MOPA, an SC with 30.6-W output average power and an extremely wide spectrum of 385 nm to beyond 2400 nm is obtained.

Femtoseconds soliton mode-locked erbium-doped fiber laser based on nickel oxide nanoparticle saturable absorber

We demonstrate a femtosecond mode-locked erbium-doped fiber laser (EDFL) using a nickel oxide (NiO) as a saturable absorber (SA). NiO nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The NiO-SA shows a 39% modulation depth with a 0.04 MW/cm2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum (FWHM) of around 2.85 nm centered at 1561.8 nm. The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.

Er-doped mode-locked fiber laser with WS2/fluorine mica (FM) saturable absorber

The report presents conventional soliton operation in an anomalous-dispersion fiber laser with a novel WS2 saturable absorber (SA) based on fluorine mica (FM) substrate. Compared to organic host material such as polymer composite, FM has higher softening temperature, heat dissipation and laser damage threshold. In this work, the modulation depth (MD) and non-saturable loss (NL) of WS2/FM SA are measured to be 3.1% and 15%, respectively. By employing the SA, a stable conventional soliton mode-locked fiber laser is achieved. The repetition rate is 8.2MHz and the pulse duration is 830fs. The fiber laser works in mode locking operation for at least ten days and no damage of the SA is observed. The results indicate that WS2/FM material is an ideal SA for Er-doped fiber (EDF) lasers.