Nonlinear Fiber Optics Research Papers (original) (raw)

2025, Optical and quantum electronics

This research investigates the utilization of a modified version of the Sardar sub-equation method to discover novel exact solutions for the generalized Pochammer Chree equation. The equation itself represents the propagation of longitudinal deformation waves in an elastic rod. By employing this modified method, we aim to identify previously unknown solutions for the equation under consideration, which can contribute to a deeper understanding of the behavior of deformation waves in elastic rods. The solutions obtained are represented by hyperbolic, trigonometric, exponential functions, dark, dark-bright, periodic, singular, and bright solutions. By selecting suitable values for the physical parameters, the dynamic behaviors of these solutions can be demonstrated. This allows for a comprehensive understanding of how the solutions evolve and behave over time. The effectiveness of these methods in capturing the dynamics of the solutions contributes to our understanding of complex physical phenomena. The study's findings show how effective the selected approaches are in explaining nonlinear dynamic processes. The findings reveal that the chosen techniques are not only effective but also easily implementable, making them applicable to nonlinear model across various fields, particularly in studying the propagation of longitudinal deformation waves in an elastic rod. Furthermore, the results demonstrate that the given model possesses solutions with potentially diverse structures.

2025, arXiv (Cornell University)

We investigate the time evolution of the photon-detection probability at various output ports of an all-fiber coupled cavity-quantum-electrodynamics (cavity-QED) system. The setup consists of two atoms trapped separately in the field of two nanofiber cavities that are connected by a standard optical fiber. We find that the normal-mode picture captures well the main features of the dynamics. However, a more accurate description based on the diagonalization of a non-Hermitian Hamiltonian reveals the origin of small yet significant features in the spontaneous emission spectra.

2025

The fibers with dispersion varying along length have important applications in optical signal processing such as high-quality optical pulse compression, coherent continuum generation, nonlinear dynamic dispersion compensation and other... more

2025, Annalen der Physik

The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering‐based nonlinearity, the random birefringence of a fiber, and the pump‐to‐signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence‐induced resonance‐like enhancement of the gain fluctuations (stochastic anti‐resonance) accompanied by pulse broadening and rare events in ...

2025

Time domain analysis is performed on the ultra-short pulsed beam propagating through the fiber bragg grating (FBG) structures. Widely known one way Beam Propagation Method (BPM) is formulated in time domain and applied on the uniform and non-uniform FBG structures. Spectral analysis, which is one of the noteworthy benefit of the TD analysis, is performed from pulsed beam at different stages, and consequently, transmission and reflection coefficient is analyzed. Dimensions of the FBG structures are chosen from the FimmProp software tools used for the same kind of structures, and compared thereof. A satisfactory comparative results are found while doing the comparison.

2025, IEEE Photonics Technology Letters

The spectral characteristics of cross-phase modulation (XPM) in multispan intensity-modulation direct-detection optical systems were investigated both experimentally and theoretically. XPM crosstalk levels and its spectral features were found to be strongly dependent on fiber dispersion and optical signal channel spacing. Interference between XPM-induced crosstalk effects created in different amplified fiber spans is also found to be important to determine the overall frequency response of XPM crosstalk effects.

2024

Saktioto and Prof. Dr. Jalil Ali for all their guidance and support throughout the duration of this research and thesis writing. I am greatly indebted to them for the knowledge imparted and the precious time they allocated to guide me. Dr. Saktioto provided the overall framework of this studies. I would like to extend my sincere appreciation to my family especially mom and dad for their tender support, morally and financially. I would also like to thanks to members of the Institute of Advanced Photonics and Sciences (APSI) for their assistance. They had provided me with ample information, cooperation and help during the process of conducting my research.

2024, Physical Review Letters

The nonlinear propagation of light pulses in liquid-filled photonic crystal fibers is considered. Due to the slow reorientational nonlinearity of some molecular liquids, the nonlinear modes propagating inside such structures can be approximated, for pulse durations much shorter than the molecular relaxation time, by temporally highly-nonlocal solitons, analytical solutions of a linear Schrödinger equation. The physical relevance of these novel solitary structures, which may have a broad range of applications, is discussed and supported by detailed numerical simulations.

2024, Photonics Research

Dissipative solitons emerge as stable pulse solutions of nonintegrable and nonconservative nonlinear physical systems, owing to a balance of nonlinearity, dispersion, and loss/gain. A considerable research effort has been dedicated to characterizing amplitude and phase evolutions in the spatiotemporal dynamics of dissipative solitons emerging from fiber lasers. Yet, the picture of the buildup process of dissipative solitons in fiber lasers is incomplete in the absence of corresponding information about the polarization evolution. Here, we characterize probabilistic polarization distributions in the buildup of dissipative solitons in a net-normal dispersion fiber laser system, mode-locked by single-wall carbon nanotubes. The output optical spectra under different pump powers are filtered by a tunable filter, and are detected by a polarization state analyzer. The laser system operates from random amplified spontaneous emission into a stable dissipative soliton state as the cavity gain is progressively increased. Correspondingly, the state of polarization of each spectral wavelength converges towards a fixed point. To reveal the invariant polarization relationship among the various wavelength components of the laser output field, the phase diagram of the ellipticity angle and the spherical orientation angle is introduced. We find that, within the central spectral region of the dissipative soliton, the state of polarization evolves with frequency by tracing a uniform arc on the Poincaré sphere, whereas in the edges of the dissipative soliton spectrum, the state of polarization abruptly changes its path. Increasing cavity gain leads to spectral broadening, accompanied by a random scattering of the state of polarization of newly generated frequencies. Further increases of pump power result in dissipative soliton explosions, accompanied by the emergence of a new type of optical polarization rogue waves. These experimental results provide a deeper insight into the transient dynamics of dissipative soliton fiber lasers.

2024, International Journal of Research -GRANTHAALAYAH

In this work we investigated propagation of ultrashort laser pulses in Tellurite glass codoped Er3+/Tm3+. We derived a general propagation equation of pulses which includes the linear and nonlinear effects to all orders. We studied in the specific case of Kerr media and obtained an ultrashort pulse propagation equation called a generalized nonlinear Schrödinger equation. The impact of the third order dispersion, the higher-order nonlinear terms self-steepening, and stimulated Raman scattering are explicitly analyzed.

2024, IEEE Journal of Selected Topics in Quantum Electronics

In this paper, the properties of nonsilica glasses and the related technology for microstructured fiber fabrication are reviewed. Numerical simulation results are shown using the properties of nonsilica microstructured fibers for mid-infrared (mid-IR) supercontinuum generation when seeding with near-IR, 200-fs pump pulses. In particular, bismuth glass small-core fibers that have two zero-dispersion wavelengths (ZDWs) are investigated, and efficient mid-IR generation is enabled by phase-matching of a 2.0-µm seed across the upper ZDW into the 3-4.5 µm wavelength range. Fiber lengths considered were 40 mm. Simulation results for a range of nonsilica large-mode fibers are also shown for comparison.

2024, Journal of Computational and Theoretical Nanoscience

Impact of such terms as third order dispersion, self-steepening and stimulated Raman scattering on evolution of ultrashort pulses is considered in detail. Under influence of these effects, pulse did not maintain its initial shape in the case of the silica fiber. Pulse splits into constituents, its spectrum also evolving into several bands which are known as optical shock and self-frequency shift phenomena. We concluded that when the input peak power is large enough, dynamics of pulse splitting will be complicated. We propose in this article, a new generation of the fiber type; the Ti:sapphire crystal fiber which is able to solve these problems of writings before. Our numerical simulations were in good agreement with the Ti:sapphire crystal fiber One basing itself on the resolution of the nonlinear Schrödinger equation.

2024

Soliton refers to highly stable localized solutions of certain nonlinear partial differential equations describing physical phenomenon. Soliton concept was first discovered on hydrodynamics in the 19th century and then entered into other branches in physics.An optical soliton in a short high amplitude optical pulse that does not spread as it propagates. It propagates through a nonlinear optical medium without any changes in its shape and velocity.Solitons in nonlinear optical fiber have important applications in communication, optical computing, optical switching etc.

2024, arXiv (Cornell University)

It is shown that sufficiently large periodic modulations in the coefficients of a nonlinear Schrödinger equation can drastically impact the spatial shape of the Peregrine soliton solutions: they can develop multiple compression points of the same amplitude, rather than only a single one, as in the spatially homogeneous focusing nonlinear Schrödinger equation. The additional compression points are generated in pairs forming a comb-like structure. The number of additional pairs depends on the amplitude of the modulation but not on its wavelength, which controls their separation distance. The dynamics and characteristics of these generalized Peregrine soliton are analytically described in the case of a completely integrable modulation. A numerical investigation shows that their main properties persist in nonintegrable situations, where no exact analytical expression of the generalized Peregrine soliton is available. Our predictions are in good agreement with numerical findings for an interesting specific case of an experimentally realizable periodically dispersion modulated photonic crystal fiber. Our results therefore pave the way for the experimental control and manipulation of the formation of generalized Peregrine rogue waves in the wide class of physical systems modeled by the nonlinear Schrödinger equation.

2024, IEEE Photonics Technology Letters

2024, Journal of Lightwave Technology

2024, Journal of the Optical Society of America B

Recently we have proposed using periodically-spaced, phase sensitive optical parametric ampli ers to balance linear loss in a nonlinear ber-optic communication line Opt. Lett. 18, 803 (1993)]. Here we present a detailed analysis of pulse propagation in such a ber line. Our analysis and numerical simulations show that the length scale over which the pulse evolution occurs is signi cantly increased beyond a soliton period. This is because of the attenuation of phase variations across the pulse's prole by the ampli ers. Analytical evidence is presented which indicates that stable pulse evolution occurs on length scales much longer than the soliton period. This is con rmed through extensive numerical simulation, and the region of stable pulse propagation is found. The average evolution of such pulses is governed by a fourthorder nonlinear di usion equation which describes the exponential decay of arbitrary initial pulses onto stable, steady-state, soliton-like pulses.

2024, Journal of the Optical Society of America B

2024, Physical Review E

We study the stability and interactions of chirped solitary pulses in a system of nonlinearly coupled cubic Ginzburg-Landau (CGL) equations with a group-velocity mismatch between them, where each CGL equation is stabilized by linearly coupling it to an additional linear dissipative equation. In the context of nonlinear fiber optics, the model describes transmission and collisions of pulses at different wavelengths in a dual-core fiber, in which the active core is furnished with bandwidth-limited gain, while the other, passive (lossy) one is necessary for stabilization of the solitary pulses. Complete and incomplete collisions of pulses in two channels in the cases of anomalous and normal dispersion in the active core are analyzed by means of perturbation theory and direct numerical simulations. It is demonstrated that the model may readily support fully stable pulses whose collisions are quasi-elastic, provided that the group-velocity difference between the two channels exceeds a critical value. In the case of quasi-elastic collisions, the temporal shift of pulses, predicted by the analytical approach, is in semi-quantitative agrement with direct numerical results in the case of anomalous dispersion (in the opposite case, the perturbation theory does not apply). We also consider a simultaneous collision between pulses in three channels, concluding that this collision remains quasi-elastic, and the pulses remain completely stable. Thus, the model may be a starting point for the design of a stabilized wavelength-division-multiplexed (WDM) transmission system.

2024, Journal of Lightwave Technology

A method for fabrication of a new type of optical fiber with dispersion varying along the fiber length is described. The main optical parameters of a drawn fiber are theoretically studied and experimentally measured. These fibers are of great interest for nonlinear fiber optics. Such applications of the fibers, such as high-quality soliton pulse compression, soliton pulsewidth stabilization through compensation of losses, and generation of a high-repetition-rate train of practically uninteracting solitons, are considered.

2024, Physical review

Optical temporal solitons, arising from self-phase modulation and negative quadratic (β 2) dispersion, are Galilean invariant, and therefore their properties do not depend on their group velocity. This is no longer true for pure-quartic soliton pulses arising from quartic (β 4) dispersion, for which a change in group velocity necessarily leads to nonzero quadratic and cubic (β 3) dispersion. Analyzing the generalized nonlinear Schrödinger equation for such dispersion relations analytically and numerically, we find that pure-quartic solitons are members of a larger family traveling at other speeds. These solitons, which appear to be stable, have a complex phase structure and have an asymmetric spectrum. Our results extend the understanding of solitons arising from high orders of dispersion.

2024, Optics Express

We theoretically present a design of self-starting operation of microcombs based on laser-cavity solitons in a system composed of a micro-resonator nested in and coupled to an amplifying laser cavity. We demonstrate that it is possible to engineer the modulationalinstability gain of the system's zero state to allow the start-up with a well-defined number of robust solitons. The approach can be implemented by using the system parameters, such as the cavity length mismatch and the gain shape, to control the number and repetition rate of the generated solitons. Because the setting does not require saturation of the gain, the results offer an alternative to standard techniques that provide laser mode-locking.

2024, Physical review

A recently observed stable regime in the form of periodically colliding counterpropagating wave packets (pulses) in an annular convection channel at very small positive overcriticalities is described analytically in terms of coupled Ginzburg-Landau equations. First, the existence of this regime is demonstrated in the framework of the simplest system including only the group-velocity difference, weak gain, and nonlinear dissipative coupling between two modes. In this approximation, the shape of the counterpropagating waves remains indefinite. It is demonstrated that additional dispersive terms, regarded as a small perturbation, provide shaping of the wave packets and also give rise to the deviation of the phase velocity from that for purely linear waves.

2024, Physical review

As is known, a solitary pulse in the complex cubic Ginzburg-Landau (GL) equation is unstable. We demonstrate that a system of two linearly coupled GL equations with gain and dissipation in one subsystem and pure dissipation in another produces absolutely stable solitons and their bound states. The problem is solved in a fully analytical form by means of the perturbation theory. The soliton coexists with a stable trivial state; there is also an unstable soliton with a smaller amplitude, which is a separatrix between the two stable states. This model has a direct application in nonlinear fiber optics, describing an Erbium-doped laser based on a dual-core fiber.

2024, arXiv (Cornell University)

2024, Nature Communications

The fractional Schrödinger equation (FSE)—a natural extension of the standard Schrödinger equation—is the basis of fractional quantum mechanics. It can be obtained by replacing the kinetic-energy operator with a fractional derivative. Here, we report the experimental realisation of an optical FSE for femtosecond laser pulses in the temporal domain. Programmable holograms and the single-shot measurement technique are respectively used to emulate a Lévy waveguide and to reconstruct the amplitude and phase of the pulses. Varying the Lévy index of the FSE and the initial pulse, the temporal dynamics is observed in diverse forms, including solitary, splitting and merging pulses, double Airy modes, and “rain-like” multi-pulse patterns. Furthermore, the transmission of input pulses carrying a fractional phase exhibits a “fractional-phase protection” effect through a regular (non-fractional) material. The experimentally generated fractional time-domain pulses offer the potential for designi...

2024, Chaos, Solitons & Fractals

We investigate experimentally and theoretically effects of the inter-core propagation mismatch on nonlinear switching in dual-core high-index-contrast soft-glass optical fibers. Incident femtosecond pulses of various energy are fed into a single ("straight") core, to identify transitions between different dynamical regimes, viz., inter-core oscillations, self-trapping in the cross core, and retaining the pulse in the straight core. The transfer between channels, which has solitonic character, is controlled by the pulse's energy. A model based on the system of coupled nonlinear Schrödinger equations reveals the effect of the mismatch parameter and pulse duration on the diagram of the various

2024, IEE Proceedings - Optoelectronics

A simple and intuitive TLM algorithm has been developed to model nonlinear optical phenomena in photonic bandgap structures such as fibre Bragg gratings. The method is used to simulate periodic nonlinear media having a Kerr nonlinearity. Many phenomena occuring in these devices, such as bistable switching, soliton propagation and limiting, are modelled and discussed. The numerical time-domain approach gives valuable insight into the behaviour of these devices.

2024, Natural Science

We propose broad supercontinuum spectrum generating highly nonlinear photonic crystal fiber (HN-PCF) which can be used in ultrahighresolution optical coherence tomography and optical transmission systems. Using full vector finite difference method, we investigated the different properties of HN-PCF. Broadband supercontinuum spectrum is numerically calculated by using nonlinear Schrödinger equation. Investigation showed that it is possible to obtain longitudinal resolution in a biological tissue of 1.3 μm, 1.2 μm and 1.1 μm by using picosecond continuum light at center wavelengths of 1.06 μm, 1.31 μm and 1.55 μm, respectively.

2024, IEEE Photonics Journal

In this paper, we first measure fiber nonlinear Kerr coefficient of a two-mode fiber (TMF) by characterizing the four-wave mixing (FWM) components. Based on the measured nonlinear coefficient, we present an analysis of the link capacity for a two-mode fiber. It is shown that despite strong spatial overlapping of the three modes, the overall capacity approaches three times of that of a single-mode fiber.

2024, Optics Express

We report on the experimental demonstration of a white-light supercontinuum generation in normally dispersive singlemode air-silica microstructured fiber. We demonstrate that the simultaneous excitation of the microstuctured fiber in its normal and anomalous dispersion regimes using the fundamental and second harmonic signals of a passively Qswitched microchip laser leads to a homogeneous supercontinuum in the visible range. This pumping scheme allows the suppression of the cascaded Raman effect predominance in favor of an efficient spectrum broadening induced by parametric phenomena. A flat supercontinuum extended from 400 to 700 nm is achieved.

2024, Advances in Optical Technologies

The paper reviews the current status and designs of all-optical gates. Various schemes with and without semiconductor optical amplifiers are discussed and compared. The optical gates are classified according to their design structures. It is divided into two major divisions that is, nonsemiconductor optical amplifier based gates and semiconductor optical amplifier based gates. In nonsemiconductor optical amplifier based gates, different schemes have been proposed to create non-linearity which is discussed. The semiconductor optical amplifier based gates of different design structures are discussed to show the probe pulse that is modulated in different ways to obtain results.

2024, Optics Communications

2024, Latvian Journal of Physics and Technical Sciences

Methods for Estimation of Optical Fiber Non-Linearity Using Self-Phase Modulation Effect Due to ever increasing channel density in WDM systems the nonlinear optical effects in fibers become a limiting factor for the high-speed data transmission, which necessitates determination of such important characteristic as the coefficient of optical nonlinearity. To measure it, two methods are proposed: continuous wave self-phase modulation (CW-SPM) and pulse phase self-modulation (P-SPM). The research work has been carried out both in the form of calculations and experimentally, taking as wavelength the central one from the third optical transparency window, λ = 1550 nm. Based on the OptSim 5.2 simulations and experimental results, the sought-for nonlinear coefficients have been calculated. In the paper, comparative analysis and estimation of the results are performed for two different optical fibers.

2024, Journal of the Optical Society of America B

Maxwell's equations for the apparently complicated generation and propagation of femtosecond four-wavemixing signals in optically thick samples can be solved by triple Fourier transformation into the threedimensional (3D) frequency domain. Given the linear absorption and refractive-index spectra, the propagation problem can be solved in three dimensions under the assumption that nonlinear distortions of the excitation pulses can be neglected. A propagation function exactly incorporates the linear evolution of the excitation pulses, the nonlinear generation of the signal, and the linear propagation of the signal. A quantitative treatment of the directional filtering of the 3D susceptibility that arises from excitation with noncollinear pulses and selective interference detection of signal in one phase-matched direction is developed. This 3D treatment is used to examine the influence of phase-matching bandwidth, directional filtering, and sample absorption on femtosecond four-wave-mixing signals in the rectangular and square boxcars phase-matching geometries.

2024, Optics Communications

The three-waveguide nonlinear directional coupler switching characteristic is studied using the eigenmodes of the structure (i.e. supermodes). This model, which is more exact than the one used in previous works, has allowed to confirm the three waveguide configuration as an alternative to the two waveguide nonlinear coupler. Moreover, an analytical expression for the critical power at which the switching between the output branches occurs has been found.

2024, arXiv (Cornell University)

Dissipative solitons are remarkable localized states of a physical system that arise from the dynamical balance between nonlinearity, dispersion and environmental energy exchange. They are the most universal form of soliton that can exist in nature, and are seen in farfrom-equilibrium systems in many fields including chemistry, biology, and physics. There has been particular interest in studying their properties in mode-locked lasers producing ultrashort light pulses, but experiments have been limited by the lack of convenient measurement techniques able to track the soliton evolution in real-time. Here, we use dispersive Fourier transform and time lens measurements to simultaneously measure realtime spectral and temporal evolution of dissipative solitons in a fiber laser as the turn-on dynamics pass through a transient unstable regime with complex break-up and collision dynamics before stabilizing to a regular mode-locked pulse train. Our measurements enable reconstruction of the soliton amplitude and phase and calculation of the corresponding complex-valued eigenvalue spectrum to provide further physical insight. These findings are significant in showing how real-time measurements can provide new perspectives into the ultrafast transient dynamics of complex systems.

2024, Conference on Lasers and Electro-Optics

We demonstrate that the pump's spatial input profile can provide additional degrees of freedom in tailoring at will the nonlinear dynamics and the ensuing spectral content of supercontinuum generation in highly multimoded optical fibers. Experiments and simulations carried out at 1550 nm indicate that the modal composition of the input beam can substantially alter the soliton fission process as well as the resulting Raman and dispersive wave generation that eventually lead to supercontinuum in such a multimode environment. Given the multitude of conceivable initial conditions, our results suggest that it is possible to pre-engineer the supercontinuum spectral content in a versatile manner.

2024, Conference on Lasers and Electro-Optics

We demonstrate over two octaves supercontinuum generation in a graded index multimode fiber using a picosecond microchip laser at 1064 nm. Enhanced visible supercontinuum is obtained in a tunable fashion based on initial launching... more

2024, Physical Review Letters

We investigate the spatial dynamics of optical necklace beams in Kerr media. For powers corresponding to less than the critical power for self-focusing per bead, we experimentally confirm the confinement of these necklace beams as proposed in [Phys. Rev. Lett. 81, 4851 (1998)]. At higher powers, we observe a transition from collective necklace behavior to one in which the beads of the necklace collapse independently. We observe that, below the transition power, the perturbed necklace still behaves in a collective manner with coupling between individual beads but that, at higher powers, it undergoes a similar transition to a decoupled state of the necklace.

2024, Proceeding on CLEO'97

2024, Electronics

The development and implementation of continuous-wave (CW) or pulsed lasers has become essential in all areas of science and engineering. In the case of pulsed lasers, their emission period is commonly set up by the length of the laser cavity, which implies that it is necessary to replace the whole laser or modify the cavity to change the repetition rate. On the other hand, microcontrollers, capable of performing specific tasks saving size, cost and power consumption, have proven to be a powerful tool for various applications. To the best of our knowledge, we present a novel pulsed laser based on a very low-cost commercial microcontroller and a continuous-wave laser diode, where the pulse width and period are adjustable through a graphical user interface (GUI); besides, a new temporal asynchronous regime consisting of periodic packets of multiple pulses is produced. Pulses from 8 to 60 ms duration and with periods from 0.25 to 5 s are presented. These long optical pulses can be usef...

2024, Optics Express

We report an original noise-like pulse dynamics observed in a figure-eight fiber laser, in which fragments are continually released from a main waveform that circulates in the cavity. Particularly, we report two representative cases of the dynamics: in the first case the released fragments drift away from the main bunch and decay over a fraction of the round-trip time, and then vanish suddenly; in the second case, the subpackets drift without decaying over the complete cavity round-trip time, until they eventually merge again with the main waveform. The most intriguing result is that these fragments, as well as the main waveform, are formed of units with sub-ns duration and roughly the same energy..

2024, Laser Sources and Applications

We study numerically and experimentally multiple-wavelength operation of an erbium-doped figure-eight fiber laser including a multiple-bandpass optical filter formed by two concatenated fiber tapers. Both continuous-wave and pulsed operations are considered. In the continuous-wave regime, stable long-term operation at multiple closely spaced wavelengths is only obtained if fine adjustments of the cavity losses are performed. Under these conditions, simultaneous lasing at up to four wavelengths separated by 1.5 nm was observed experimentally. Tunable singlewavelength operation over more than 20 nm is also observed in the continuous-wave regime. In the passive mode locking regime, numerical simulations indicate that mechanisms involving the filter losses and the nonlinear transmission characteristic of the NOLM contribute in principle to stabilize dual-wavelength operation, allowing less demanding cavity loss adjustments. In this regime, the problem of synchronization between the pulse trains generated at each wavelength adds an additional dimension to the problem. In presence of cavity dispersion, the pulses at each wavelength tend to be asynchronous if the wavelength separation is large, however they can be synchronous in the case of closely spaced wavelengths, if cross-phase modulation is able to compensate for the dispersion-induced walkoff. Experimentally, fundamental and 2 nd-order harmonic mode locking was observed, characterized by the generation of noise-like pulses. Finally, a regime of multi-wavelength passive Q-switching was also observed. We believe that this work will be helpful to guide the design of multiple-wavelength fiber laser sources, which are attractive for a wide range of applications including Wavelength Division Multiplexing transmissions, signal processing and sensing.

2024, Applied Optics

We propose and study experimentally and numerically a passively mode-locked figure-eight fiber laser scheme generating noiselike optical pulses, or subns wave packets with a fine inner structure of subps pulses presenting random amplitudes and durations. The particular design of the nonlinear optical loop mirror (NOLM) used in this laser, relying on nonlinear polarization rotation, allows adjusting the switching power through input polarization control. Experimental results show stable pulsed operation over a limited range of the NOLM input polarization angle. Interestingly, the spectral and temporal characteristics of these pulses are observed to be widely variable over that range. In particular, the spectral width varies from 16 to 52 nm and this spectral variation is associated with an inverse evolution in the durations of the bunch and of the inner ultrashort pulses. Simulation results are in good agreement with the experiment. They confirm the strong dependence of the pulse properties on the value of the NOLM switching power, although NOLM switching is not alone responsible for the appearance of the noiselike pulsing mode.

2024, Applied Optics

Propagation constants of the guided modes of symmetric and asymmetric slab guides are known. Kogelnik and Ramaswamy 1 have given transcendental equations and curves for the normalized constant b. Broadening, or compression, of ultrashort pulses is determined by group velocity disper sion (GVD). This has been calculated for weakly guiding circular fibers by Gloge. 2 With the recent advances in the production of ultrashort pulses, down to the 10-fs range, and with production of picosecond pulses from diode lasers, GVD in slab guides becomes increasingly of interest. For pulses as short as 20-100 fs, significant GVD occurs at a distance of the order of only a few centimeters. Thus manipulation and modification of ultrashort pulses in planar geometry guides are becoming possible. In this Letter, we calculate the GVD in weakly guiding asymmetric slab guides. The results can be used to find broadening of ultrashort pulses in these guides. Additionally, it is shown that, for asymmetric guides, negative (anomalous) GVD can be obtained in the single-mode regime. We consider an asymmetric slab guide with indices of the cover, film, and substrate n c , n ƒ , and n s , respectively, and film thickness t. We assume a weakly guiding case, i.e., that n ƒn s = Δn « n ƒ ,n s ,n c , but that n ƒ-n c can be fairly large. For this case, the group velocity dispersion is the sum of the guide and material dispersions: where

2024, Journal of Physics B

Self-compression of femtosecond laser pulses and more than an order of magnitude increase of the peak intensity is found in a positive dispersion medium in low dispersion regime based on the (3+1)-dimensional nonlinear Schrödinger... more

2024, Journal of Physics B: Atomic, Molecular and Optical Physics

2024, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

Various techniques are described for the generation of high repetition rate highquality soliton pulse trains in the range 10 GHz-1 THz. Emphasis is placed on the technique of nonlinear conversion of an optical beat signal in dispersion-modified fibre. This can be achieved by a number of methods, including tapered or dispersiondecreasing fibre, step-like dispersion-profiled fibre and comb-like dispersion-profiled fibre. In addition, self-Raman scattering has been demonstrated as a powerful tech nique for ultrashort pulse generation and excellent mark space ratio operation. Tech niques based on phase-modulated sideband extraction and direct modulation using electroabsorption modulators operating in the 10-60 GHz regime are also described.

2024, J. Opt. Commun.

In this paper, simulative performance analysis for different modulation formats like NRZ rectangular, NRZ raised cosine, RZ soliton, RZ super gaussian, RZ raised cosine and RZ rectangular, has been demonstrated and analyzed at each node with varying bit rate. It is seen that overall NRZ modulation is performing better among all modulation driving schemes. It is also observed that by using RZ soliton format system can exist up to 90 dB of insertion loss of optical add drop multiplexers with bit rate upto 10 Gbit/s. For 10 Gbit/s of bit rate quality factor drops off below 15 dB after 85 dB of insertion loss for RZ soliton.