Soliton Switching Research Articles

Switching and transformation of multi-state solitons in a slightly normal dispersion mode-locked fiber laser

Passively mode locked fiber lasers are excellent platforms for soliton generation. Here, multi-state switchable behaviors in a slightly normal dispersion mode-locked fiber laser are experimentally demonstrated with an identical configuration. A saturable absorber based on single-wall carbon nanotube is served as mode-locking device and an intrinsic birefringence spectral filtering is employed as a tunable inline filter. Consequently, with properly modifying pumping powers and orientations of polarization controller paddles, the operation regimes of the proposed laser could be reversibly switched between dissipative solitons and amplifier similaritons, and the characteristics of intermediate states are recorded. Tunable dissipative solitons with a tuning range of 38 nm and noise-like pulses could also alternatively be generated. This multi-state behavior switching could be attributed to the strong filtering caused by the limited gain bandwidth under strong pump strength. The experimental observations of these multi-state switchable transitions may offer insight into the pulse regime dynamics in the near-zero dispersion region and offer flexibility in multi-functional designs of the laser configuration, which would enable innovations in nonlinear optics and its applications.

All-Optical Switches for Optical Soliton Interactions in a Birefringent Fiber

Interactions among optical solitons can be used to develop photonic information processing devices such as all-optical switches and all-optical logic gates. It is the key to achieve high-speed, high-capacity all-optical networks and optical computers, which is also important in academy. We study the properties of all-optical switches of optical solitons in birefringent fibers, based on the coupled nonlinear Schrödinger equations. It is found that under different initial conditions we can achieve all-optical switching functions. We also study the influence of different physical parameters of birefringent fibers on all-optical soliton switching. The relevant conclusions are conducive to achieving the all-optical switching function of optical solitons in birefringent fibers, providing useful guidance for widespread applications of optical soliton all-optical switches in birefringent fibers of communications.

Dynamics of twin pulse propagation and dual-optical switching in a Λ + Ξ atomic medium

Optical bistability (OB) and optical multistability (OM) as well as optical soliton and all-optical switching have been successfully established in a lambda + cascade-type five-level atomic medium under electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) regimes. For this configuration, three laser fields are required to excite atomic transitions. The probe laser field with two circularly left- and right-polarized components excites atoms in a lambda-type configuration. Meanwhile, two coupling laser fields excite atoms in a ladder-type configuration. In this way, the above optical phenomena can occur with two frequency channels corresponding to the circularly left- and right-polarized light components. By adjusting the strength/direction of the static magnetic field in the presence of the driving field, the EIT and EIA effects can be swapped, at the same time, OB and OM effects can also be converted. In the EIT regime, the propagation of the probe pulse easily achieves the soliton state, whereas it can be completely extinguished in the EIA regime. This makes it easy to create an all-optical switching mechanism. Especially, both components of the probe field (cw) can be modulated into a synchronous or asynchronous square pulse according to the modulation of the driving field. The results obtained from the investigated model may provide merits of the applications for optical storage and all-optical switching for multi-channel optical communications.

Switching and vector characteristics of bound-state solitons in a graphene-based mode-locked fiber laser

A passive mode-locked erbium-doped fiber laser based on graphene operating in the anomalous dispersion state is designed in this paper. In this experiment, the complete convert process from traditional soliton pulses to soliton rains and bound-state (BS) soliton pulses, and ultimately to traditional soliton pulses, is achieved by adjusting the pump power and polarization controller (PC) to control factors such as nonlinearity, dispersion, and birefringence in the cavity. In the BS soliton state, switching between the 0 phase and π phase BS solitons is achieved. We also replaced the 20/80 coupler with the 30/70 coupler to achieve the soliton rains by varying the energy alteration of the intracavity pulse. When the pump power is increased to 350 mW, the laser generates multi-pulses and eventually forms a new BS. In addition, we also studied the soliton vector characteristics during this conversion process and found the polarization-locked vector soliton (PLVS). The research results enrich nonlinear vector soliton dynamics and provide valuable data for further theoretical studies.

Nonautonomous three soliton interactions in an inhomogeneous optical fiber: Application to soliton switching devices

We investigate the interactional behavior of three nonautonomous solitons in an optical fiber with inhomogeneous nature which can be described by nonlinear Schrödinger equation with nonautonomous term. A pair of matrices constructed with the aid of AKNS procedure for nonautonomous NLS equation with variable coefficients. Based on the Lax pair, three soliton solutions are generated by employing Darboux method. We show the switchable characteristics of nonautonomous three solitons by typical graphical illustration. The remarkable results presented in this study can be used to design the optical logic gate devices for optical computing.

Self-regulating soliton switching waves in microresonators

Dissipative soliton Kerr frequency combs in microresonators have recently been demonstrated with the self-injection locking process. They have the advantage of turnkey deterministic comb generation and simplifying dark soliton generation in the normal dispersion regime. Here, the formation process of dark pulses triggered by self-injection locking is studied by regarding them as a pair of domain walls that connect domains having different intracavity powers. The self-injection locking mechanism allows the domain walls to self-regulate their position so that a wide range of dark comb states can be accessed, and the duty cycle is controlled by the feedback phase. Direct imaging of the dark pulse shape using the electro-optic sampling technique is used to verify the theory. The results provide new physical insights as well as a new operational modality for this important class of nonlinear waves.

Bistable soliton switching dynamics in a PT -symmetric coupler with saturable nonlinearity

We investigate the switching dynamics in a $\mathcal{PT}$-symmetric fiber coupler composed of a saturable nonlinear material as the core. In such a saturable nonlinear medium, bistable solitons may evolve due to the balance between dispersion and saturable nonlinearity, which we extend in the context of the $\mathcal{PT}$-symmetric coupler. Our investigations of power-controlled and phase-sensitive switching show richer soliton switching dynamics than the currently existing conventional counterparts, which may lead to ultrafast and efficient all-optical switching dynamics at very low power owing to the combined effects of $\mathcal{PT}$ symmetry and saturable nonlinearity. In addition to the input power, the relative phase of the input solitons and saturable coefficient are additional controlling parameters that efficiently tailor the switching dynamics. Also, we provide a suitable range of system and pulse parameters that would be helpful for the practical realization of the coupler to use in all-optical switching devices and photonic circuits. Finally, we develop a variational approach to analytically investigate the switching dynamics in such $\mathcal{PT}$-symmetric couplers that excellently predicts the numerical findings.

Nonlinear switching of optical solitons in fiber Bragg gratings with non-instantaneous Kerr nonlinearity

Introduction:Optical soliton switching in nonlinear uniform fiber Bragg gratings with non-instantaneous Kerr nonlinearity is numerically investigated. Two cases of pulse propagation are considered: propagation through the reflection and transmission regions. Objectives:The purpose is to investigate the influence of a delayed response of the Kerr effect on the switching characteristics of uniform fiber Bragg gratings and compare to the instantaneous nonlinear regime. Methods:A modified set of nonlinear coupled mode equations are numerically resolved on a two-dimensional grid using an implicit four-order Runge–Kutta method. Results:It is found that the reflectivity of the gratings only depend on the relaxation time of the grating medium when the input pulse intensity reaches a certain level. In addition, marked differences in shape of the reflected and transmitted pulses are observed.

Ultrafast dynamic RF-spectrum investigation of soliton microcombs

Dissipative Kerr solitons in microcavity systems exhibit remarkable nonlinear dynamics. The real-time measurement of soliton motion facilitates the comprehensive understanding of soliton physics. In this Letter, an all-optical radio frequency (RF) spectrum analyzer (named f-LISA) is used to characterize various stable soliton states and to track relative soliton motion in real time. By applying an inverse Fourier transform to the broadband RF spectrum, the autocorrelation traces are obtained with a temporal resolution of 373 fs and an ultrahigh frame rate of 20.6 MHz. We successfully characterize not only the stable single soliton state but also the stable multi-soliton states with different azimuthal angles between adjacent solitons. Furthermore, the dynamics of soliton switching from four-soliton state to single soliton state is observed in a temporal window of 60 µs. It is believed that the proposed scheme provides an alternative way to visualize the multi-soliton trajectories and enable the study of the soliton dynamics in integrated microcavities.

Soliton Burst and Bi‐Directional Switching in the Platform with Positive Thermal‐Refractive Coefficient Using an Auxiliary Laser

AbstractDissipative Kerr solitons in optical microresonators enable the generation of stable ultrashort pulses and phase‐locked frequency combs, leading to their widespread applications. For traditional platforms with positive thermal‐refractive coefficient, strong thermal effect increases the difficulties of soliton triggering and prohibits the deterministic control of soliton number. Here, using an auxiliary laser to tune thermal effect, soliton burst and bi‐directional switching are demonstrated in high‐index doped silica glass platform. First, by varying the parameters of the auxiliary laser, the thermal effect tuning of the microresonator is studied with different thermal compensation states achieved, leading to distinct soliton switching features. Especially, the solitons burst and bi‐directional switch in over‐compensated state. The corresponding process is recorded in real time based on a temporal magnification system, uncovering transient dynamics from continuum background noise to soliton formation. Finally, the deterministic generation of solitons is enabled with controllable soliton number spanning from 1 to 21. The present work provides insight into soliton dynamics and enables soliton generation on demand with a large range of soliton numbers inside a single device.

Attosecond soliton switching through the interactions of two and three solitons in an inhomogeneous fiber

We obtain the exact two and three soliton solutions for higher order NLS equation with variable coefficients using Darboux transformation method with some algebraic manipulations based on constructed Lax Pair. For the first time, switching characteristics of two and three solitons in the attosecond regime via inelastic soliton interactions are discussed through some graphical illustrations. Additionally, effects of the inhomogeneous coefficients on propagation features of solitons are analyzed graphically. Our results have certain applications in the construction of optical switching and soliton management in optical communication systems.

All-optical switching of ultrafast solitons at 1560 nm in dual-core fibers with high contrast of refractive index

We present a study of ultrafast solitonic all-optical switching in the C-band using dual-core optical fibers fabricated in-house. The two soft glasses used for the fiber express high contrast of refractive index at the level of 0.4. The core was made of a highly nonlinear lead-silicate glass, which, combined with the anomalous dispersion, allowed the solitonic propagation at low pulse energies. A convincing switching performance was demonstrated using the optimized fiber at hundreds of picojoule level of the in-coupled energy. The dedicated numerical simulations unveiled the solitonic propagation character of 75 fs excitation pulses influenced by dual-core asymmetry. All the key parameters of the switching, such as the optimal fiber length (38 mm), the switching contrast (4.5 dB) and the switching energy levels (200–700 pJ), were confirmed by the numerical results.

Dissipative soliton dynamics and switching in split ring resonator based metamaterial with multi-photon absorption and diffusion

Compound dissipative soliton (DS) is obtained theoretically in Split Ring Resonator based metamaterial having higher order nonlinearities, multi-photon absorption and diffusion. Effects of both the multi-photon absorption and diffusion on the DS are found to be detrimental however can be compensated by a suitable external gain to stabilize the DS. The interaction dynamics of two DSs is studied for different phase difference and initial separation. The phase controlled soliton switching is demonstrated. Notably, a weak solitonic beam is demonstrated to control a strong one. The DSs are robust against the randomness of the metamaterial. The outcome of this investigation may be useful to design experiments that employ DS in higher order nonlinear metamaterials.

Optical waves/modes in a multicomponent inhomogeneous optical fiber via a three-coupled variable-coefficient nonlinear Schrödinger system

Recent progress in optical fibers is impressive, while nonlinear Schrödinger-type models are seen in fiber optics and other fields (such as ferromagnetism, plasma physics, Bose–Einstein condensation and oceanography). Hereby, our symbolic computation on a three-coupled variable-coefficient nonlinear Schrödinger system is performed, for the picosecond-pulse attenuation/amplification in a multicomponent inhomogeneous optical fiber with diverse polarizations/frequencies. For the slowly-varying envelopes of optical modes, we obtain a similarity reduction, an auto-Bäcklund transformation and some analytic solutions, which rely on the optical-fiber variable coefficients, i.e., the fiber loss/gain, nonlinearity and group velocity dispersion. Relevant variable-coefficient constraints are presented. Our results might be of some use in the construction of logic gates, optical computing, soliton switching, design of fiber directional couplers, quantum information processing, soliton amplification in the wavelength division multiplexing systems, solitonic studies in the all-optical devices and birefringence fiber systems.

Dark soliton steering in PT-symmetric couplers with third-order and intermodal dispersions

We demonstrate steering dynamics of dark solitons in a parity–time ( P T )-symmetric nonlinear directional coupler (NLDC) in the presence of third-order dispersion (TOD) and intermodal dispersion (IMD). A complete switch with an excellent efficiency at a very low critical power, even lower compared to the bright soliton switching, has been observed. The numerical results show that both TOD and IMD have no effect on soliton steering in P T -symmetric couplers with coupling length π / 2 . But, as we increase the coupling length to 2 π , IMD shows marginal effects for dark soliton steering in P T -symmetric couplers, while TOD shows no impact. Additionally, we have also studied the phase-controlled switching in P T -symmetric couplers with two different coupling lengths and demonstrated its advantage over the power-controlled one.

Reversible ultrafast soliton switching in dual-core highly nonlinear optical fibers.

We experimentally investigate a nonlinear switching mechanism in a dual-core highly nonlinear optical fiber. We focus the input stream of femtosecond pulses on one core only, to identify transitions between inter-core oscillations, self-trapping in the cross core, and self-trapping of the pulse in the straight core. A model based on the system of coupled nonlinear Schrödinger equations provides surprisingly good agreement with the experimental findings.

Transition from bird to butterfly shaped nonautonomous soliton and soliton switching in erbium doped resonant fiber

Through theoretical approach, two soliton solutions for nonautonomous inhomogeneous nonlinear Schrödinger - Maxwell Bloch (INLS-MB) equation is attained with the aid of Darboux transformation technique. Based on obtained solutions, bird and butterfly like wave pattern are attained for the specific choice of inhomogeneous coefficients. Especially, by means of dispersion management scheme, exponential profile is adopted for the dispersion coefficient in the governing two soliton solutions. Also, through the appropriate choices of control parameters in inhomogeneous function, the transition from bird shaped to butterfly shaped pulse is observed astoundingly. Finally, nonautonomous soliton switching achieved through soliton fission and fusion phenomenon which could be observed via properly manipulating dispersion and nonlinearity parameters. The obtained analytical results and graphical illustrations are may helpful for the design of soliton control system in fiber optic communication and soliton based optical switching.

Self-starting bi-chromatic LiNbO3 soliton microcomb

For its many useful properties, including second and third-order optical nonlinearity as well as electro-optic control, lithium niobate is considered an important potential microcomb material. Here, a soliton microcomb is demonstrated in a monolithic high-Q lithium niobate resonator. Besides the demonstration of soliton mode locking, the photorefractive effect enables mode locking to self-start and soliton switching to occur bi-directionally. Second-harmonic generation of the soliton spectrum is also observed, an essential step for comb self-referencing. The Raman shock time constant of lithium niobate is also determined by measurement of soliton self-frequency-shift. Besides the considerable technical simplification provided by a self-starting soliton system, these demonstrations, together with the electro-optic and piezoelectric properties of lithium niobate, open the door to a multi-functional microcomb providing f-2f generation and fast electrical control of optical frequency and repetition rate, all of which are critical in applications including time keeping, frequency synthesis/division, spectroscopy and signal generation.

Switching a Dirac soliton by a weak signal in binary waveguide arrays with varying propagation mismatch

We numerically study the switching of the discrete Dirac solitons in binary waveguide arrays with the increase of absolute value of the propagation mismatch parameter along the longitudinal axis. We demonstrate that the Dirac soliton will be compressed in the transverse direction during propagation and will finally be localized in just one waveguide. We show that although at the input the system is completely symmetric, at the output the symmetry can be broken if the propagation mismatch parameter and the nonlinearity coefficient have different signs. In this case, with a very weak signal initially added at the input, we can switch the Dirac soliton from one waveguide to another. Meanwhile, if they are of the same sign, then the compression process of the Dirac solitons will be very stable, and the symmetry of the Dirac soliton profile will be conserved during propagation.

Soliton-impurity interaction in two coupled ferromagnetic chains

The propagation of soliton excitations in a system of two magnetic chains with impurities is studied. The inhomogeneous chains coupled through ferromagnetic interaction between the opposite spins are described by a Heisenberg model in the nearest-neighbor approximation. The presence of the impurities leads to linear perturbing terms in the evolutionary equations. We investigated numerically the influence of the soliton parameters, the interchain coupling and the defect strength on the soliton dynamics. The conditions of perfect soliton switching are obtained.