Polarization-locked Vector Solitons Research Articles

Optical Nonlinearity of Violet Phosphorus and Applications in Fiber Lasers

A D-shaped fiber is coated with a new two-dimensional nanomaterial, violet phosphorus (VP), to create a saturable absorber (SA) with a modulation depth of 3.68%. Subsequently, the SA is inserted into a fiber laser, enabling successful generation of dark solitons and bright–dark soliton pairs through adjustment of the polarization state within the cavity. Through further study, mode-locked pulses are achieved, proving the existence of polarization-locked vector solitons. The results indicate that VP can be used as a polarization-independent SA.

Polarization dynamics of vector solitons in a fiber laser.

We investigate the polarization dynamics of vector solitons in a fiber laser mode-locked by a saturable absorber (SA). Three types of vector solitons were obtained in the laser, including group velocity locked vector solitons (GVLVS), polarization locked vector solitons (PLVS), and polarization rotation locked vector solitons (PRLVS). Their polarization evolution during intracavity propagation is discussed. Pure vector solitons are obtained from the continuous wave (CW) background by soliton distillation, and the characteristics of the vector solitons without and with distillation are analyzed, respectively. Numerical simulations suggest that the features of vector solitons in a fiber laser could be assemble to those generated in fibers.

Experimental study of single-shot polarization dynamics of dual dissipative solitons

The state of polarization provides an additional dimension to the pulse dynamics of dissipative solitons. However, due to lack of appropriate measuring instruments, the polarization evolution of dual pulse vector solitons is still unclear. Here, for an erbium-doped fiber laser mode-locked with carbon nanotubes, we characterize the single-shot polarization evolution of dual dissipative solitons in detail using a high-speed wave-resolved measurement technique. For the different birefringence distributions in the laser cavity, the coupling between the orthogonal components of the vector soliton has a great influence on its physical properties, which may lead to various physical images of the vector soliton. We observed typical polarization-locked vector solitons and polarization attractors in the dual soliton pulses. We also observed that the polarization dynamics of the lead and tail vector pulses have similar evolution dynamics on the Poincaré sphere, while they have a distinct phase difference. By virtue of the difference of the processing SOPs between the leading and trailing pulses, we resolve three kinds of two solitons pulses with distinct relative phase evolutions. Our results enrich the vector soliton dynamics in fiber lasers.

CoS nanosheets for generation of vector soliton and bound solitons in nonlinear optical fiber system

Transition metal chalcogenides (TMCs) with two-dimensional (2D) structures are of great interest for their extraordinary electrical, optical, magnetic, and mechanical properties. In this work, a novel cobalt sulfide (CoS) nanosheets (NSs) based saturable absorber (SA) with a modulation depth of 6.4 % is fabricated through liquid phase exfoliation (LPE) method, and successfully applied to a passive mode-locked erbium-doped fiber laser (PML-EDFL) for the first time as far as we know. By adjusting the pump power and optimizing the orientation of the intra-cavity polarization controller, a stable conventional solitons (CS) pulse with a duration of 905 fs and signal-to-noise ratio (SNR) of 58.5 dB at fundamental repetition frequency of 4.03 MHz, a pair of bound solitons with time interval of 4.9 ps between two 1.8 ps pulses are generated in proposed PML-EDFL. Meanwhile, the vector characteristics of generated soliton pulse are investigated, and polarization-locked vector solitons are observed. The results reveal that the CoS NSs have superior polarization insensitive nonlinear optical modulation properties and will find extensive application potential in the ultrafast photonics.

Tantalum disulfide nanosheets for the generation of polarization domain wall solitons and polarization locked vector solitons

Tantalum disulfide (TaS2) has been employed for catalysis and optical switch due to its tunable band gap, strong photoluminescence, and controllable size. However, its nonlinear optical response and applications in ultrafast optics have not been exploited. In this work, TaS2 based saturable absorber (TaS2-SA) is prepared, which exhibits strong saturable absorption characteristics with modulation depth of 8.5%. Based on the TaS2-SA, polarization domain wall solitons and polarization locked vector solitons are successfully realized. To the best of our knowledge, this is the first study of the polarization characteristics of TaS2 based fiber lasers. Our findings suggest that TaS2 is a promising nonlinear optical material and provide a valuable method for the development of TaS2 based ultrafast photonic devices.

Vector soliton generation from a compact all-polarization-maintaining fiber laser

We investigate polarization-locked vector solitons (PLVSs) arising in an all-polarization-maintaining (PM) soliton fiber laser mode-locked by a carbon nanotube. The laser can operate stably in both Q-switched and mode-locked states with different pump power. Under the PLVS condition, we observe a string of peak-dip-pair sidebands after polarization-resolving measurement, indicating the strong and regular energy exchange between the two polarized orthogonal components, which evidently distinguishes this all-PM fiber laser from conventional single-mode fiber-based vector cavities. By dispersion compensating, vector dissipative solitons are also successfully obtained. The cavity structure is greatly simplified and stabilized by a hybrid fiber component and shows excellent long-term stability.

Vector features of pulsating soliton in an ultrafast fiber laser.

Pulsating soliton in ultrafast fiber lasers has interesting non-stationary dynamics, which is one of the hot topics in field of nonlinear soliton. So far, most researchers only focused on the spectral and temporal characteristics of pulsating soliton. However, the vector features of pulsating soliton were rarely studied. In this work, we experimentally studied the pulsating vector solitons in an ultrafast fiber laser. Three categories of vector solitons with different polarization evolution characteristics could be obtained by adjusting the pump power and polarization controller, such as pulsating polarization-locked vector soliton (PLVS), pulsating polarization-rotation vector soliton (PRVS) and progressive pulsating PRVS. Interestingly, besides the basic polarization rotation with a period of 2 roundtrips, the polarization angle also evolves with progressive mode in the progressive pulsating PRVS state. The abundant results of pulsating vector solitons demonstrate that investigating vector features of nonlinear soliton dynamics is necessary and significant and would greatly enrich the research of soliton dynamics.

Manipulation of parabolic polarization- and group-velocity- locked vector solitons

In this manuscript, we report the simulation about manipulating parabolic polarization-locked and group-velocity-locked vector solitons in a polarization resolved fiber system. Through changing input pulse parameters of orthogonal polarization modes, output temporal pulse shapes and corresponding optical spectra are simulated. For the case of polarization-locked vector soliton, fundamental parabolic vector soliton always appears except when projection angle is changed. While for group-velocity-locked vector soliton, pseudo-high-order parabolic vector solitons can be achieved through changing phase difference and projection angle, and maintain fundamental soltion state although other two pulse parameters (amplitude ratio and time delay) are changed.

Dynamic polarization attractors of dissipative solitons from carbon nanotube mode-locked Er-doped laser

Abstract We report experimental observation of polarization attractors in the form of vector dissipative solitons from a carbon nanotube mode locked fiber laser. At a time scale of 14–14,000 roundtrips, the typical polarization locked vector solitons, and other appealing attractors are shown. In addition, we observe the vector dissipative solitons operated in dual-wavelength regime with central wavelength of 1533 and 1557 nm which can be related to a fixed point polarization attractor. The results unveiled complex oscillatory behavior of dissipative solitons in the polarization domain which may help understand laser physics, nonlinear optics. The demonstrated work may underpin a new type of high energy laser source leading to possible applications in nanoparticle manipulation, micromachining, spectroscopy etc.

Manipulation of polarization- and group-velocity-locked dark vector solitons

In this manuscript, we simulate the manipulation of polarization- and group-velocity-locked dark vector solitons. Through changing pulse parameters of incident dark vector solitons, different kinds of pulse shapes could be generated. For incident fundamental dark polarization-locked vector soliton (PLVS), “2 + 2” pseudo-high-order dark PLVS and bright-dark PLVS could be generated. While for incident fundamental dark group-velocity-locked vector soliton (GVLVS), dark vector solitons with multiple side dips could be achieved depending on input pulse parameters.

Generation of pseudo-high-order polarization-locked vector solitons with super-Gaussian pulses

In this paper, we simulate the generation of pseudo-high-order polarization-locked vector solitons (PLVSs) based on fundamental super-Gaussian PLVS. Through changing pulse chirp, pulse amplitude, projection angle, phase difference and time delay of incident pulses, different kinds of pseudo-high-order PLVS with the same central wavelength can be achieved in a polarization resolved fiber system.

Manipulation of Gaussian derivative pulses and vector solitons in fiber lasers with analytic modeling by the coupled complex Ginzburg–Landau equations

Both positive- and negative-polarity Gaussian monocycle and doublet pulses, for which the pulse shapes are the first and second derivatives of Gaussian functions plus some continuous-wave backgrounds respectively, are generated in a ring-cavity erbium-doped fiber laser from polarization-locked vector solitons by using passive optical technology. The pulse states are switchable and are found to be the superposition of bright and dark solitons with different widths, amplitudes, time delays, polarizations, and wavelengths. Qualitative analysis of the properties of vector solitons are performed by solving coupled complex Ginzburg–Landau equations, and analytic modeling of the fiber laser is presented. By representing the envelopes of bright soliton by sech- and dark soliton by tanh-based functions, the incoherent superposition of these two soliton components have simulated the experimental observations, and the underlying mechanisms for the formation of monocycle and doublet pulses are attributed to the polarization locking of bright and dark solitons. The theoretical modeling is used to calculate the pulse parameters of the fiber laser, and the intracavity birefringence can be estimated. The results of tunable optical vector solitons are compared with atomic solitons in the system of Bose–Einstein condensation. Since the governing equations for soliton generation in fiber lasers and Bose–Einstein condensation have many properties in common, thus the simulation and propagation of pulsating waves may open a new route to explore the classical solitary dynamics in nonlinear optics and its quantum analogy in ultracold fields.

Observation of chaotic polarization attractors from a graphene mode locked soliton fiber laser

We have demonstrated an all-fiber passively mode locked erbium-doped fiber laser (EDFL) based on graphene–polyvinyl-alcohol film. By watchfully adjusting the polarization controller, two different polarization attractors, including polarization locked vector solitons and a circular attractor, can be observed. This is first time, to the best of our knowledge, to explore the dynamics polarization attractors exhibited by a vector soliton generated from an EDFL based on graphene.

Polarization-multiplexed, dual-comb all-fiber mode-locked laser

Mode-locked fiber lasers that can simultaneously generate two asynchronous ultrashort pulse trains could play an attractive role as the alternative light sources for low-complexity dual-comb metrology applications. Although a few multiplexing schemes to realize such lasers have been proposed and demonstrated, here we investigate the lasing characteristics of a passively mode-locked fiber laser with a finite amount of intracavity birefringence. By introducing a section of polarization-maintaining (PM) fiber into the otherwise-non-PM-single-mode cavity, dual asynchronous pulses with nearly orthogonal states of polarization are generated. With a repetition rate difference of hundreds of hertz, the pulses have well-overlapped spectra and show typical features of polarization-locked vector solitons. It is demonstrated that under an anomalous or net normal dispersion regime, either dual vector solitons or dual dissipative vector solitons can be generated, respectively. Such polarization-multiplexed single single-cavity dual-comb lasers could find further uses in various applications in need of simple dual-comb system solutions.

Generation of Polarization-Locked Vector Solitons in Mode-Locked Thulium Fiber Laser

In this paper, we report polarization-locked vector soliton (PLVS) generation in a linear thulium-doped fiber laser. The fiber laser was composed of all-anomalous-dispersion fibers, passively mode-locked with a semiconductor saturable absorber mirror. Approximately 1.2-ps single vector soliton pulses centered at 2023.7 nm were generated. Extra “peak-dip” spectral sidebands were clearly visible in the polarization-resolved optical spectra, indicating coherent energy exchange between the two polarization components of the vector solitons. In addition, multiple-PLVS operation modes were experimentally investigated, and our experimental results were confirmed by numerical simulations. To the best of our knowledge, this is the first observation of polarization-locked single vector soliton generation operating in the 2-μm spectral range.

Polarization Domains and Polarization Locked Vector Solitons in a Fiber Laser

We have experimentally observed, for the first time, the coexistence of polarization domains (PDs) and polarization locked vector solitons (PLVSs) in an Er-doped fiber laser with microfiber-based graphene as a saturable absorber (SA). Taking advantage of the high nonlinearity and the saturable absorption of the microfiber-based graphene SA, we observed both PDs and their splitting into regularly or irregularly distributed multiple PDs under relatively high pump power; at lower pump power with careful adjustment of the intra-cavity polarization controllers, we observed PLVSs either as disordered soliton bunch or with harmonic mode locking. The conditions under which these patterns formed have also been experimentally investigated in detail.

Black phosphorus saturable absorber for dual-wavelength polarization-locked vector soliton generation

We report the usage of few-layered black phosphorus (BP) as saturable absorbers (SAs) to achieve dual-wavelength vector solitons mode locking in an erbium-doped fiber laser for the first time, to our knowledge. The SA is fabricated based on liquid exfoliation method by incorporating BP nanosheets with polyvinyl alcohol. We have demonstrated that the saturable absorption of BP is polarization independent. The laser is capable of generating dual-wavelength polarization-locked vector solitons centered at ~1533 and ~1558 nm with the bandwidths of ~3.7 and ~6.9 nm simultaneously. The results indicate the potential applications of few-layered BP as broadband SAs in vector soliton pulses generation.

Wavelength tunable L Band polarization-locked vector soliton fiber laser based on SWCNT-SA and CFBG

Wavelength tunable L-Band polarization-locked vector soliton fiber laser based on single-walled carbon nanotube saturable absorber (SWCNT-SA) and chirped fiber Bragg grating (CFBG) is presented for the first time. By inserting the SWCNT-SA into an all-fiber laser cavity, polarization-locked vector solitons (PLVS) are obtained. The CFBG glued on a plastic cantilever is used for wavelength tuning. By mechanically bending the cantilever, the center wavelength of the PLVS pulses can be continuously tuned from 1606.8 nm to 1614 nm, while the polarization-locked state is kept stable. The properties and dynamics of PLVSs are experimentally investigated and stable PLVS operation including high-order PLVSs is demonstrated. The pulse width and repetition rate are 7.06 ps and 11.9 MHz at a wavelength of 1611 nm, respectively. This work demonstrates the feasibility of using polarization-insensitive CFBG to realize wavelength tuning in PLVS fiber laser.

Above 100 nJ solitons from a passively mode-locked thulium-doped fiber oscillator

AsbtractWe report on stable nanosecond pulses with a non-symmetrical shape and high energy from a passively mode-locked thulium (Tm) fiber oscillator in the purely anomalous dispersion regime. The laser generated wave-breaking-free solitons with pulse widths increased from ~460 ps to ~3.15 ns by boosting the pump strength. The solitons yielded an output average power of ~1.1 W, a repetition rate of 10.63 MHz, and a pulse energy up to ~103 nJ at the maximum available pump power. By removing the free-space components, the pulse energy was further scaled to ~268 nJ at a 11.2 MHz repetition rate. The corresponding polarization-locked vector solitons (PLVS) were also observed.

Polarization-locked vector solitons in a mode-locked fiber laser using polarization-sensitive few-layer graphene deposited D-shaped fiber saturable absorber

We have experimentally demonstrated polarization-locked vector soliton generation in a passively mode-locked erbium-doped fiber laser by using a few-layer graphene deposited D-shaped fiber to act as a saturable absorber (SA). Due to the long light/graphene interaction length and the asymmetric structure, the SA used in this work has large polarization-dependent loss, and as a result, the stationary polarization-locked vector solitons can be generated, being different from the scalar solitons produced by the nonlinear polarization rotation technique. The formation mechanism of such solitons is studied and it is found that they are elliptically polarized solitons.