bluuebunny/crossref_metadata_2025 huggingface dataset:
Dispersion of the Two-Photon Absorption Coefficient in a Silica Optical Fiber
Authors: MIZUNAMI Toru , TAKAGI Keiji
Published: February 2023

Recently investigations of the nonlinear optical properties of silica fibers in the ultraviolet region have been promoted by the development of medical applications of ultraviolet lasers such as excimer lasers. In the wavelengths less than ~310 nm, twice the photon energy corresponds to the band edge of fused silica. Therefore two-photon absorption occurs as well as in germanosilicate or lead-glass fibers in the blue-green region. The two-photon absorption of ultraviolet radiation induces intensity-dependent loss, which is serious for short-pulse lasers. Further, defects are more or less generated by two-photon absorption, which degrade the fibers. So that, it is important to clarify the characteristics of two-photon absorption, especially the dispersion.
Dielectric Tensor of Photoinduced Polarization Convertors in Optical Fibers
Authors: Kamal A. , Russell P. St. J.
Published: February 2023

In this paper, the general form of the dielectric tensor induced in glass by interferometric exposure to light of arbitrary polarization is derived using a Hamiltonian approach for one and two-photon absorption. Considerable research effort has been devoted to the fabrication of polarization convertors in optical fibers using anisotropic photosensitivity [1-4], partly because of their potential applications in distributed sensing. The analysis of these devices has been conducted by writing down the dielectric tensor using phenomenological arguments. A rigorous development of the complete dielectric tensor starting from the microscopic origins has been lacking in the literature. We discuss the physical origins of anisotropic photosensitivity and develop a model based on preferential ionization to arrive at the form of the dielectric tensor under general exposure conditions. Both single and two-photon processes can be treated, making the formulation valid for both UV side-writing and in-core filter writing with blue/green guided modes. In addition to elucidating the dielectric tensor of polarization convertors, the treatment predicts that a special new type of light tap will form during single-photon side-writing with waves of linear but orthogonal polarization states.
Stable Trains of Brillouin Solitons Generated by a CW-Pumped Fiber Ring Laser.
Authors: MONTES Carlos , BOTINEAU Jean , HÖÖK Anders , LEGRAND Olivier , LEYCURAS Claude , MAMHOUD Abdellatif , PICHOLLE Eric
Published: February 2023

Stimulated Brillouin scattering (SBS), studied since 1976 in cw-pumped fiber ring lasers [1], yields either steady or pulsed regimes. Ultracoherent cw-Stokes output has been obtained for strong quality factors [2], but with moderate finesse these cw-pumped resonators are essentially unstable [3] [4]. Bursting oscillations and chaos appear for small enough feedback [5], but up to now no generic scenario has been suggested for the generation of stable Brillouin pulses. Recent observation of dissipative superluminous solitons in a Brillouin fiber ring laser [6], whose nonlinear dynamics is described through the coherent three-wave SBS model, raises the question of a physical mechanism giving birth to such intense and short coherent structures under a cw-pumping regime.
Patterns and Spatio-Temporal Complexity of Stimulated Brillouin Scattering in Multi-mode Optical Fibre
Authors: Harrison R.G. , Lim D.S. , Lu Weiping , Yu D.J.
Published: February 2023

Pattern formations and spatio-temporal complexity are currently a focus of considerable interest in the area of nonlinear dynamics. In optics these phenomena may arise from the competition between local nonlinearity and diffraction and/or dissipation of the system. In this report we provide first observations of rich spatial and spatio-temporal phenomena in stimulated Brillouin scattering generated in c.w pumped multi mode optical fibre.
Direct observation of picosecond pulse chirps influenced by copropagating stimulated Raman scattering signal in optical fiber
Authors: Emplit Ph. , Hamaide J.-P.
Published: February 2023

During linear propagation through a single-mode optical fiber, a picosecond pulse is essentially affected by the fiber attenuation and the group-velocity dispersion (GVD), which respectively result in a wavelength-independent loss of power and a temporal pulse broadening. These both linear processes do not perturb the width of the pulse spectral power density. When increasing the pulse intensity nonlinear propagation will generally result in a modification of its initial spectral density. Among the large variety of nonlinear effects already observed in fibers [1], the combined actions of self-phase modulation (SPM), due to the temporal intensity dependence of the core refractive index, and stimulated Raman scattering (SRS) in silica, generating a Stokes signal at a shifted wavelength, have received much attention during the recent years because of their potential implications in fiber transmission systems, in optical pulse compression arrangements or in Raman fiber laser devices. Stolen et al. [2] succesfully described Raman gain as a response function in the time domain. This approach permits to globally treat the pump and Stokes signals propagation, but it is essentially applicable for ultrashort pulses (<100 fs) when pump bandwidth is of the order of the Raman shift. For longer pulses, simple theoretical models were proposed [3-5] to simulate the individual propagation of two interacting pump and Stokes pulses in the presence of walk-off that gradually separates the pulses because of GVD. In this simplified schemes, the Raman frequency shift is reduced to its peak value (440 cm−1) and a related effective gain is considered.
Low-Latency Soliton Logic Gate in a Rapidly Amplifying Fiber
Authors: Barnett B. , Islam M.N.
Published: February 2023

Guided-wave optical devices are important for serial high-speed processing, particularly when information enters or exits in optical format. Optical logic gates permit "intelligence" or decision-making capability to be introduced into optical transmission or network systems. We show numerically that an all-optical, cascadable, low-energy, soliton logic gate with a fan-out of 2.7 and an energy contrast of 5.5 can be made in a moderately birefringent erbium-doped fiber amplifier (EDFA) that is one soliton period long. The switching results from large frequency shifts associated with cross-phase modulation, birefringent walk-off and 8dB of bandwidth-limited gain. For sub-picosecond pulses and EDFA's with a zero dispersion wavelength between 1.4 and 1.5 microns, one soliton period corresponds to between 5 and 20m of fiber. In contrast, typical nonlinear optical loop mirrors [1] or soliton-dragging logic gates [2] use between 300m and several kilometers of fiber to accumulate slowly a phase or timing shift, resulting in a latency of at least several microseconds and a sensitivity to environmental changes.
Modulation Instability and the Stability and Switching of Spatial Solitons in a Pair of Identical Planar Waveguides
Authors: Boardman AD , Xie K
Published: February 2023

In a recent investigation of the displacement suffered by two spatial solitons approaching each other some general coupled equations were used1-3. They describe the complete nonlinear interaction between two spatial solitons, with the same frequency and polarisation, located in a pair of, identical, coupled slab waveguides (1 and 2) and have the form, where propagation is along the z-axis, beam confinement by the nonlinearity is along the x-axis, modal confinement is along the y-axis, k = 3-i, i = 1,2, ψi and ψk are normalised slowly varying amplitudes of the electric fields in the guides, ν represents the inter-guide coupling and μ1, μ2 are nonlinear coefficients. The first point to make is that these coupled equations go far beyond the classical work of Jensen4 and will only return to it5 provided that the last four terms are neglected. Indeed, some of the usually neglected terms are larger than the terms that are, normally, retained and, therefore, have a crucial influence on the stability and the threshold powers of the spatial solitons. The second point is that a full variational solution of the coupled equations can be made to yield a mathematical, analytical, nonlinear stability analysis, generating switching formulae with tractable forms for the stability edges, or thresholds. Even within a Jensen model, the results to be presented here are entirely new and it should be stressed that all the parameters ν, μ1 and μ2 are required for inter-guide interactions. A Jensen formalism, on the other hand, involving ν and only one other parameter μ, is adequate for intra-guide polarisation interactions. The objectives here are (a) to present a mathematical and numerical solution of the general coupled equations that will account for energy exchange between spatial solitons (b) to generate a theory of stability for solitons hovering, one above the other, in the respective guides (c) to investigate the possibilities for modulation instability.
Method for the Determination of the Resonant Group Velocity Dispersion in Erbium Doped Fiber Lasers
Authors: Fontana F. , Bordogna G. , Grasso G. , Romagnoli M. , Midrio M. , Franco P.
Published: February 2023

Whenever an optical signal is tuned into a resonance such as a band pass filter or a laser transition, a dispersion arising from the resonance starts playing a role on the propagation of the signal. The effect of the dispersion on the signal depends on few parameters such as the dispersion spectral width, the amplitude or the strength of the interaction of the signal with the resonance. In long haul optical telecommunication systems, a certain number of optical ampifiers are required to restore the depletion of the optical, signal caused by the filer losses. Neverthless the effect of the resonant group velocity dispersion (GVD) provided by the amplifiers plays a minor role as long as non zero GVD for the link is chosen. More critical is the effect of the resonant GVD in erbium doped fiber lasers (EDFL's) where the length of the active medium may, in principle, coincide with the the length of the cavity. The effect of a spectrally varying GVD profile is that of distorting the temporal profile of a pulse during the propagation [1]. In the soliton fiber lasers the temporal asymmetry provided by the resonant dispersion is partially compensated by the restoration of the nonlinear gain, and eventually the ultimate pulse duration differs from the natural limit imposed by the gain bandwidth.
Nonclassical Properties of Active Directional Coupler
Authors: Janszky J. , Sibilia C. , Bertolotti M.
Published: February 2023

Recently a number of papers has been devoted to the behaviour of nonlinear directional coupler when a third order[1,2] or secon order nonlinearity is present inside the structure [3].
443nm blue Cerenkov SHG in a pNAn-PVA waveguide
Authors: Kinoshita T. , Tsuchiya K. , Sasaki K. , Yokoh Y. , Ashitaka H. , Ogata N.
Published: February 2023

Application of nonlinear materials have been restricted by cutoff wavelength. Most of organic crystals and polymers containing dye chromophors have longer cutoff wavelengths than inorganic crystals.
Numerical Modeling of PE:LiNbO3 Integrated Optical Parametric Oscillators in Quasi-Phase Matching Configuration
Authors: Baldi P. , Aschieri P. , Nouh S. , De Micheli M.P. , Ostrowsky D.B. , Shenoy M.R. , Delacourt D. , Papuchon M.
Published: February 2023

The only Integrated Optical Parametric Oscillator1 (IOPO), reported to date was realized using Ti Indiffusion in LiNbO3, functionned at 250°C, and was pumped with a pulsed dye laser operating at 0.6 μm. In this paper we use a numerical model to show that the use of periodically poled2,3,4 LiNbO3 with proton exchanged guides should permit operation of efficient parametric amplifiers and oscillators at ambiant temperature, using CW diode laser or mini-YAG pumps, and having signal and idler beams in the 1.3 and 1.55 μm telecommunication windows.
Spatial Solitons Caused by Cascaded Second-Order Nonlinearity
Authors: Schiek Roland
Published: February 2023

After the early proposal of self-trapped optical beams [1] only some years ago the interest in spatial solitons as building blocks for all-optical devices has increased [2], [3], [4]. Because of the lack of materials with large electronic non-resonant third-order susceptibilities the following problem for the application of fast χ(3) processes arises: the product of the required light intensity and the interaction length becomes large. In order to relax this requirement, recently the use of a new cascaded second-order nonlinear refraction has been proposed to support the direct third-order nonlinear refraction [5], [6]. It was theoretically shown that important χ(3) effects like temporal soliton propagation, nonlinear switching, and soliton switching will work on the basis of the cascaded χ(2): χ(2) nonlinearity with reduced light intensities.
Measurement of a Fast Nonlinear Refractive Index Coefficient in an Er-doped Fiber Induced by a 527-nm Pumping
Authors: Lee Hak Kyu , Kim Kyong Hon , Park Seo Yeon
Published: February 2023

The optical nonlinear processes at near absorption resonance in an Er-doped fiber have been considered as larger and much slower processes than those in normal single mode fibers[1]. Recently, however, M. L. Stok et al. showed an evidence of fast nonlinear responses in an Er-doped fiber by gererating 900 fs optical pulses at 1.5-μm by the cross phase modulation in their synchronously pumped mode-locked Er-doped fiber laser experiment[2]. In this presentation, we report a measurement method and measured results on fast responses of the nonlinear refractive index, n2, in an Er-doped fiber for pumpingat 527-nm wavelength by using a modified Sagnac interferometric method.
The Stability of a Waveguide Ring Laser with a Nonlinear Directional Outcoupler
Authors: Karpierz Mirosław A. , Szczepański Paweł , Weinert-Rączka Ewa
Published: February 2023

Recently, the waveguide ring lasers made in erbium-doped-fiber technology [1] or in semiconductor integrated optics [2] have attracted attention because of the simplicity of fabrication and the elimination of the need for high quality mirrors. Potential applications of such lasers contain high-speed communication systems as well as optical computing and data processing.
All Single-Mode Synchronously Mode locked Erbium-Ytterbium Fiber Laser Pumped with a Nd:YAG Laser
Authors: Stock M. L. , Yang L.-M. , Andrejco M. J. , Fermann M. E.
Published: February 2023

All-optical active mode locking is currently of great interest for the generation of high-repetition rate pulse trains[1] and in all-optical clock-recovery circuits[2], which are some of the key components of ultra-high bit rate communication systems[3]. Though active mode locking has been known for some 30 years[4], only recently has the advent of high-quality single-mode rare-earth-doped fibers[5] enabled the replacement of the electronic modulator with its all-optical equivalent. In this technique an optical control pulse is used to periodically perturb the phase of the fiber (or waveguide) laser via cross-phase modulation. By the generation of side-bands the laser modes of the signal may then be locked to produce an all-optical equivalent of FM mode locking.
Dynamic spatial solitons
Authors: Snyder A. W. , Hewlett S. J. , Mitchell D. J.
Published: February 2023

We consider the expanded class of one- and two-dimensional spatial solitons that exist when the soliton is a compound entity composed of two orthogonal beams [1-3]. These solitons propagate in a homogeneous isotropic medium whose refractive index has an arbitrary dependence on intensity. As with classical solitons, their intensity profile remains axially uniform but, in addition, their polarization state now changes continuously with propagation. We refer to this new class of self-guided waves as ‘dynamic solitons’ because of their internal field dynamics. Dynamic solitons can have an arbitrary number of intensity peaks and thus exhibit novel intensity profiles. Their common salient property is that they are composed of two orthogonal beams, neither of which is, in general, a soliton on its own. Each beam is, however, a mode of the (axially uniform) linear optical waveguide induced by the dynamic soliton.
The use of GaInAsP amplifiers for 40 Gbit/s signal processing.
Authors: Ellis A.D. , Spirit D.M.
Published: February 2023

Optical time domain multiplexed (OTDM) systems are expected to play an important role in increasing the aggregate fibre capacity in telecommunications networks beyond the levels attainable with electronic systems. Within these systems, one of the key elements is a flexible optical demultiplexer, and recently attention has been focused on the use of the Kerr effect in silica based fibres to produce optically controlled switching elements1,2. However, whilst offering attractive functionality, the relatively low nonlinear coefficientin silica fibres leads to excessively long devices and consequent latency, timing and stability issues. It is also necessary to carefully select the fibre properties and signal wavelengths for these switches to achieve a desired function. Thus a compact sub millimetre device, offering similar overall levels of nonlinearity offers clear advantages.
Efficient Quasi-Phase-Matched Generation of Parametric Fluorescence in Room Temperature Lithium Niobate Waveguides
Authors: Baldi P. , Aschieri P. , Nouh S. , de Micheli M. , Ostrowsky D.B. , Delacourt D. , Banti X. , Papuchon M. , Tartarini G. , Bassi P.
Published: February 2023

We report efficient waveguided, quasi-phase-matched, parametric fluorescence at 1.2 to 2.5 microns at ambient temperature, using an 800 nm pump and correlate our experimental results with theoretical predictions.
Generation of high-power femtosecond optical pulses by chirped pulse amplification in erbium doped fibers
Authors: Stock M. L. , Galvanauskas A. , Fermann M. E. , Mourou G. , Harter D. J.
Published: February 2023

As femtosecond fiber oscillator development matures yielding reliable, daily-use sources of ultrashort pulses[1,2], the focus of current research is increasingly directed towards their applications. To this end we have created a highly-efficient, high-power fiber oscillator/fiber amplifier based source of femtosecond pulses operating in the telecommunication band of 1.55μm, producing pulses with an energy content of 1.4 nJ. This demonstration shows the promise of fiber amplifiers for the generation of ultra-high power pulses.
Ultrahigh-speed optical soliton communication and soliton transmission control
Authors: Nakazawa Masataka
Published: February 2023

In 1989 it was shown that erbium-doped fiber amplifiers (EDFAs) are very useful for soliton amplification and transmission.1 Since then, many interesting results were reported and the soliton transmission technology has matured considerably through the use of EDFAs.1~4 These amplifiers have been used to develop a new soliton communication method (Dynamic soliton, Guiding-center soliton, or Average soliton) for sending solitons over long distances using lumped optical amplifiers. The lumped amplifier technique using EDFAs made it possible to move the soliton communication into the developmental stage. This technique has a wide range of applicability from La (amplifier spacing) << Zsp (soliton period) to La~Zsp, depending on the maximum required transmission distance.
Acoustic Effect And The Polarization Of Adjacent Bits In Soliton Communication Lines
Authors: Golovchenko E. A. , Pilipetskii A. N.
Published: February 2023

One of the main mechanisms that limits the bit rate and transmission distance in soliton communication lines is the so called “long-range” interaction of solitons [1]. The physical reason of this interaction is the electrostrictional excitation of the acoustic waves by light pulses and back-influence of the acoustic wave on solitons [2]. In soliton communication lines the interaction of solitons with the acoustic wave results in the additional to the Gordon-Haus effect [3] timing jitter of solitons [4,5]. Although the timing jitter of solitons can be significantly reduced by guiding filters [6], the detailed investigation of the acoustic effect is still important because the guiding filters cannot totally suppress the timing jitter.
Separation of Signal from Noise In Soliton Transmission Systems
Authors: Hasegawa Akira , Yano Tetsuya , Kodama Yuji
Published: February 2023

Use of the soliton property of amplitude dependent velocity enables one to separate signal from noise in soliton based transmission systems.
Saturated Growth of Gordon-Haus Noise in Interacting Soliton Pulse Trains
Authors: Arnold J. M.
Published: February 2023

The performance of soliton communication systems transmitting high data rates over large distances is dominated by the effects of amplified spontaneous emission ASE arising from the erbium-doped fibre amplifiers necessary to sustain the soliton energy in the presence of fibre attenuation. Previous analysis of this effect [1,2] has concentrated on the behaviour of a single soliton in the presence of cumulative amplifier noise; the classic analysis of Gordon-Haus [1] demonstrated that RMS position jitter of about 1 soliton FWHM occurred at a propagation distance of 2300 km in a system in which the soliton FWHM was 10 ps, the soliton length scale was 8 km and the amplifier gain was 1.26. This permits a BER of 10-9 if the interpulse period is 100 ps, corresponding to a bit rate of 10 Gb s−1. A critical assumption in this type of calculation is that the interpulse spacing T is large enough to neglect any interactions between solitons. The present author has shown that if x << L, where x is the normalised propagation distance and L is the stability length defined by L = (1/4)exp(T/2), then a periodic pulse train of period T behaves essentially as isolated solitons; in the Gordon-Haus calculations [1] x/L= 0.14.
Pulse Chirp of Gain-Switched Laser Diode Compensated by Narrow-Band F-P Resonator
Authors: Huang Chao , Li Shichen
Published: February 2023

Ultrashort optical pulses with high repetition can be easily generated by directly modulated laser diodes. However, this method causes large frequency chirping which limits the bandwidth-distance product for high bit rate optical communication. Because the chirp-is nonlinear, it is difficult to obtain completely transform-limited pulses by using highly dispersive single mode fiber. Nakazawa et al1 experimentally obtained the transform-limit. ed pulses from a gain-switched DFB laser diode using a narrow-band F-P resonator (FPR), and transmited these pulses as soliton source for optical soliton communication2. However, Mollenauer et al3 asserted that such a source is also very likely to be subject to significant pulse-to-pulse frequency jitter, because no amount of filtering can completely eliminate chirp. In this paper, we will consider the dispersion of FPR, and it is showed that FPR could play the role not only in filtering but also in chirp compensation for gain-switched pulses. The transform-limited pulses can be obtained by designing parameters of FPR properly.
Self Induced Couplers: Bright Soliton Beams that Travel In Parallel
Authors: Haelterman M. , Mitchell D.J. , Snyder A.W.
Published: February 2023

It is well know that two sufficiently well separated identical (bright) spatial solitons launched parallel to one another will attract each other if they are in phase, and repel each other if they are 1800 out of phase [1]. This result holds not just for planar solitons of Kerr material, but more generally for any stable self-guided beam of a medium whose refractive index depends arbitrarily on intensity [2]. Accordingly, are there any conditions under which two stable self-guided beams can travel in parallel?
Calculations of Femtosecond Temporal Solitons and Spatial Solitons Using the Vector Maxwell's Equations
Authors: Goorjian Peter M. , Joseph Rose M. , Taflove Allen
Published: February 2023

Experimentalists have produced all-optical switches capable of 100-fs responses [1]. Also, there are experimental observations [2] and theoretical calculations [3] of spatial soliton interactions. To adequately model such effects, nonlinearities in optical materials [4] (both instantaneous and dispersive) must be included. In principle, the behavior of electromagnetic fields in nonlinear dielectrics can be determined by solving Maxwell's equations subject to the assumption that the electric polarization has a nonlinear relation to the electric field. However, until our previous work [5 - 8], the resulting nonlinear Maxwell's equations have not been solved directly. Rather, approximations have been made that result in a class of generalized nonlinear Schrodinger equations (GNLSE) [9] that solve only for the envelope of the optical pulses.
Blue self-frequency shift of femtosecond optical solitons
Authors: Serkin V.N. , Vysloukh V.A.
Published: February 2023

The effect of Raman self-scattering or the red self-frequency shifting of the soliton spectrum is one of the fundamental nonlinear effect in fibers [1-8]. Experimental and theoretical investigations of this effect have been carried out up to now in standard fibres using the traditional approximation of the NSE. This approximation corresponds to spectral-homogeneous dependence of GVD on frequency. However, even the first experiments with dispersion-shifted and erbium-doped fibres [8-11] and the theoretical works on femtosecond soliton propagation in fibers with potential barrier-like shaped dispersion [12,13] pointed to the possibility of new effects.
"Spatial solitons in photorefractive crystals with local mechanism of nonlinearity"
Authors: Iturbe Castillo M. D. , Márquez Aguilar P. A. , Sánchez Mondragón J. J. , Stepanov S. , Vysloukh V.
Published: February 2023

The possibility of exciting spatial solitons using moderate power CW lasers appears promising for optical interconnects, communication, and information processing. In addition to the dye solutions (using ethanol, acetone, etc.) where the dark soliton excitation by Ar-ion lasers was reported recently (see e.g. [1]), photorefractive crystals (PRCs) [2] are also highly suitable for these applications. They show high photoinduced refractive index changes (δn≈ 10−5-10−3) at extremely low CW laser intensities (10−4 W/cm2) and allow easy switching of the sign of the optical nonlinearity (through the change of the crystal orientation, light polarization, or the sign of externally applied DC electric field) needed for observation of bright and dark solitons.
Optical Processing with Spatial Solitary-Waves in Planar Microresonators
Authors: Peschel U. , Peschel T. , Lederer F.
Published: February 2023

Recent experiments [1] and theoretical [2] research concerning nonlinear effects in planar microresonators has covered mainly all optical switching of single pixels under normal incidence, including transverse effects. Here we study a nonlinear Fabry-Perot under oblique incidence and investigate the suitability of spatial (bright) solitary waves, emerging in the transmitted field, as basic units of self trapping and binary processing.
Wave Collapse and Optical Pulse Compression
Authors: Turitsyn Sergei K.
Published: February 2023

The past several decades of development of nonlinear optics clearly demonstrated an important role playing by universal nonlinear models. Simply formulated, but, at the same time, rich in content, the models such as the nonlinear Schrödinger equation, the sine-Gordon equation, the system describing three-wave resonant interaction, and others occur in a wide variety of different physical systems. These models have much in common. All of them are based on nonlinear equations that possess stable soliton solutions. In recent years the dynamics of soliton pulses in these basic models and their numerous generalizations has been a subject of extensive investigations. The using of the nonlinear effects in optical devices has allowed the demonstration such applications of the solitons as the pulse compression, the soliton laser, long-distance soliton transmission through high-bit-rate communication systems, soliton amplification in erbium doped fibers, etc (see, e.g., [1]). From a general point of view, most of the applications of the above-mentioned and related to them models are based on such a property of nonlinear systems as the possibility of a stable soliton dynamics.
Suppression of resonances associated with periodically amplified solitons
Authors: Kelly S.M.J. , Brabec T. , Krausz F. , Elgin J.N.
Published: February 2023

Experiments have shown the presence of a spatially periodic gain/loss and/or dispersion, as experienced by a soliton pulse propagating in the distributed environment of a fibre laser (or for that matter any other equivalent system) can act as a source of instability, see [1] and references therein. In rare earth doped fibre lasers this is paricularly evident with the generation of femtosecond soliton pulses, [2,3]. A characteristic signature of this instability is the appearance of a series of well defined spectral resonances(sidebands) in the spectral wings of the pulse. These components act as an energy sink, introduce destabilising effects and also preclude full use of the gain linewidth. Theoretical studies have indicated the magnitude [4] and position [5] of these resonances scales as

≈

Z
o

Z
a

where Z
o
is the soliton period which is inversly proportional to the (net)second order dispersion and Z
a
is the fundamental period associated with the perturbation, typically the fibre (cavity)length. In principle therefore, using fibres of shorter length and/or lower dispersion should permit the generation of shorter pulses and hence more efficient use of the gain linewidth, [1,3]. With the former there is a practical limit on how short a fibre can become whereas in the latter a point is ultimately reached where higher order dispersion, in particular third order dispersion, becomes important.
Numerical study of the figure eight fiber laser
Authors: Afanasjev V. V. , Grudinin A. B.
Published: February 2023

Passively mode-locked soliton fiber lasers (PSLs) based on the Nonlinear Amplifying Loop Mirror (the figure-8 laser) have recently become of considerable interest owing to their ability to produce ultra-short pulses from a simple cavity configuration and also due to the many physical effects involved in the laser action and affecting laser output [1-3]. This laser demonstrates many interesting features such as the existence of soliton and non-soliton components in the laser output and energy quantization [4], resulting in a dependence of the number circulating pulses on laser pump power and fixed parameters for the generated pulses.
Externally Initiated Passive Mode-Locking in Fibre Laser
Authors: Khrushchev I.Yu. , Grudinin A. B. , Dianov E. M.
Published: February 2023

Passively mode - locked fibre Soliton Lasers (PSL) have recently become of considerable interest owing to their ability to produce ultrashort pulses in a simple laser cavity configuration. In addition, a lot of interesting effects are involved in the PSL operation. The mode-locking process in PSL is similar to that of a laser with a fast saturable absorber and is initiated by the most intensive fluctuation of the intracavity energy flow [1]. Another important feature of PSL is the soliton nature of the generated pulses resulting in a well-defined energy of an individual pulse [2]. Typically, PSL generates a few pulses per round-trip period, and the time interval between pulses is a random value as there is no force holding pulses at certain time distance. Nevertheless, under certain circumstancies, the laser output pattern demonstrates stability during several minutes [3].
Pulse-to-Pulse Frequency Jitter in Diode Lasers and Soliton Transmission
Authors: Mirasso C. R. , Pesquera L. , A  , .  , Mecozzi
Published: February 2023

Repeaterless transoceanic optical communication links are the subject of active research and development. Recently several groups1,2 have reported error free soliton transmission over more than the trans-Pacific distance (9,000 km) at GHz bit rates. Different techniques (passive filters2,3 and pulse retiming1) have been used to overcome the Gordon-Haus limit4 (accumulation of amplified spontaneous emission in the erbium-doped fibre amplifiers regularly spaced along the optical link). Soliton pulses have been generated from mode-locked diode lasers2 and from gain-switched diode lasers1. Mechanical instability and fixed repetition rates of mode-locked external cavity lasers seem to be a problem for practical applications. Unlike the mode-locking techniques, gain-switching does not require an extension of the laser cavity. However, its output is severly chirped and a narrow-band optical filter must be used to limit the bandwidth of the signal. Despite the fact that the τ Δ f product obtained with such a source is apparently satisfactory (0.4), gross excess pulse broadening is observed for distances greater than a few thousand kilometers5.
A split-step finite element scheme for spatio-tenporal analysis of pulse propagation in nonlinear waveguides
Authors: Buah P.A. , Rahman B. M. A. , Grattan K. T. V.
Published: February 2023

A numerical simulation technique to study the propagation of pulses in nonlinear waveguides (NLWG) with materials that exhibit Kerr or non-Kerr nonlinearities with finite time response is presented. This method is a combination of the split-step finite element method and a third-order accurate difference scheme to match the solution along the characteristic of the (z,t) plane. The simultaneous effects of integrating and higher-order nonlinearity on the stability of pulses in nonlinear waveguide structures have been examined.
High repetition rate CW dark soliton train generation in a fiber with decreasing dispersion.
Authors: Shipulin A.V. , Fursa D.G. , Golovchenko E.A. , Dianov E.M.
Published: February 2023

The non-linear Schrodinger equation (NLS) predicts an existence of stable solutions (e.g. solutions conserving amplitude and phase under propagation) for both positive and negative Group Velocity Dispersion (GVD) regions. The solution existing in the positive GVD region consist of a rapid dip in a CW background and is called a "dark soliton" analogously to a "bright soliton" for the negative GVD region [1,2]. The fundamental dark soliton is an anti- symmetric function of time, with an abrupt π phase shift and zero intensity at its center. Although the existence of dark optical solitons in fibers was first predicted in the early 1970-s, experimental verification was reported not long ago [3]. In all the experiments known to date a dip of a dark pulse existed in the intensity of a broad pulse. Another possibility of forming of dark solitons from a periodically modulated CW signal in a fiber with amplification was reported recently [4].
Electronic nonlinear optical behaviour of a polymer waveguide
Authors: Crook R. J. , Cotter N. P. K. , Sambles J. R. , Rangel-Rojo R. , Spruce G. , Wherrett B. S.
Published: February 2023

The nonlinear optical properties of polydiacetlylenes (PDA) in the solid state are of interest both from a fundamental and a technological viewpoint. The third order nonlinear optical susceptibility χ(3) for a number of these materials has been measured and the electronic nonresonant χ(3) has been found to be relatively large (> 10-11esu)1 and ultra-fast (<1ps)2. One particular PDA, poly [5,7-dodecadiyne- 1,12-diolbis(n-buto- xycarbonylmethylurethane] (P4BCMU) has received much attention due to its solubility and the ability to spin-coat the material into thin film wave- guide form. However recently Hasegawa et al3 have demonstrated that this polymer may also be thermally evaporated.
Optically Induced ElectronicNonlinearities and Passive Optical Bistability in InGaAs/InP Quantum Well Waveguides at 1.5μm
Authors: Neilson D. T. , Ehrlich J. E. , Walker A. C. , Kennedy G. T. , Grant R. S. , Sibbett W. , Hopkinson M. , Pate M.
Published: February 2023

All-optical switching phenomena within a waveguide configuration are of considerable interest for routing and signal processing applications in communications systems. Two classes of device can be identified: those dependent on non-resonant ultrafast nonlinearities, capable of switching at the data-rate of ultra-high frequency signals; and those exploiting the much lower power resonant nonlinear phenomena which, due to their slower (> 100ps) response, are suitable as data-transparent switches capable of opening or closing the desired channels within a network under optical control.
High Speed Low Power Switching of a Polarisation Rotation Gate using AlGaAs Multiquantum Well Waveguides
Authors: Snow P. A. , Day I. E. , White I. H. , Penty R. V. , Kennedy G. T. , Sibbett W. , Aitchison J. S.
Published: February 2023

Work on the development of integrated optical devices for nonlinear switching and processing has tended to focus on the performance of Mach Zehnder1 and directional coupler2 switches.
Simulation of 50GHz Transmission Over 50km of Standard Fibre using Mid-point Spectral Inversion for Dispersion Compensation
Authors: Richardson David J , Laming Richard I , Taverner Domino , Payne David N
Published: February 2023

Transmission of 6ps linear pulse pairs over 50km of standard fibre is demonstrated by employing midpoint spectral-inversion (phase conjugation) of the data signal to compensate dispersion effects. Pulse broadening as low as 10% and faithful reconstruction of the pulse patterns is observed and confirms the applicability of this technique to bit-rates greater than 100 Gbits-1.
Signal Degradation Due to Amplifier Spontaneous Emission Noise in Nonlinear Propagation Regime
Authors: Matera F. , Settembre M.
Published: February 2023

Several works have shown the possibility to transmit nonsoliton signals on very long distances when zero dispersion fibers are used. Such propagation regime requires a fine control on the GVD and exclude the possibility to use wavelength division multiple access (WDM) techniques as only one channel can work at zero dispersion wavelength.
Modulational Chaos in Periodically Amplified Fiber Links and in Fiber Lasers
Authors: Trillo S. , Wabnitz S.
Published: February 2023

The optical Kerr effect leads to modulational instability (MI) in optical fibers, which involves the periodic exchange of energy between a continuous wave (cw) at frequency ω0 and its sidebands at the frequencies = ω1,2 = ω0 ±Ω [1]. In dissipative systems such as repeaterless fiber transmission links [2] or fiber amplifiers [3], the presence of linear loss or gain modifies the spectrum of. MI gain, and the frequency conversion process is aperiodic. We show here that spatially chaotic behavior may arise in the frequency conversion whenever a modulated light field propagates in a spatially periodic fiber systems such as a periodically amplified links [4] or a ring laser [5].
Signal Degradations due to Temporal Raman Gain Variations
Authors: Rottwitt Karsten , Povlsen Jørn H. , Aakjer Thomas , Bjarklev Anders
Published: February 2023

In nonlinear long distance transmission, the distributed erbium doped fiber (d-EDF) is a promising component due to very low signal power excursions [1]. This allows a spacing between two pump power stations in the order of 100 km [1], when the pump wavelength is 1.48 μm. Thus having a signal wavelength near 1.55 μm, the background loss is canceled out by stimulated emission from both Raman scattering and erbium ions. Using a very small erbium concentration the noise figure may be minimized and transparency may be obtained for a total bidirectional pump power of around 100 mW giving noise figures near 10 dB [1],[2].
Passive Modelocking in Fiber Lasers
Authors: Menyuk C. R.
Published: February 2023

Passive modelocking is a critical tool for achieving sub-picosecond pulses, not only in fiber lasers, but in many other laser systems as well. Passively modelocked laser systems have been studied to date using two almost diametrically opposite approaches. In the first approach, which is computational, one simulates the entire evolution of light within the laser, starting from noise. In the second approach, which is analytical, one uses an idealization in which the pulse evolution during a single pass through the laser is assumed to be small to obtain a simple equation, closely related to the Ginzburg-Landau equation, which describes the evolution. One then determines the equilibria of this equation and their stability. Determining the stability is a crucial step since only stable equilibria can occur in nature; yet, it is a step that is hard to carry out analytically, and work to date1,2 has relied on approximate methods which require considerable a priori physical insight into the form that the most unstable perturbations will have.
Large Nonlinear Phase Modulation in Quasi-Phasematched KTP Waveguides Due to Cascaded Second-Order Processes
Authors: Sundheimer M.L. , Bosshard Ch. , Van Stryland E.W. , Stegeman G.I. , Bierlein J.D.
Published: February 2023

It has been known for many years that a nonlinear phase shift can be imparted on the fundamental in non-phasematched second-harmonic generation via down-conversion of the second-harmonic.1
Optimized Multilayer Design in Nonlinear Antiresonant Waveguides for Surface Normal Second-Harmonic Generation
Authors: Dai H. , Normandin R. , Janz S. , Chatenoud F. , Delage A.
Published: February 2023

Second-harmonic (SH) generation in waveguides has been extensively studied in recent years [1, 2]. One scheme that has received great attention is so-called surface-emitting second harmonic generation (SESHG) which involves nonlinear mixing of two oppositely propagating guided waves to generate coherent SH (or sum-frequency) light emitting from the waveguide surface. It has been demonstrated that a significant nonlinear harmonic conversion efficiency can be obtained in SESHG waveguides consisting of a quasi-phasematched AlxGa1-x As multilayer structure [3]. It has also been shown that these SESHG waveguides have potential applications in novel optoelectronic devices such as integrable optical correlator, picosecond signal processing device, WDM demultiplexer, optical interconnect and frequency doubler for semiconductor lasers [3-6].
Dispersion Compensated Fiber Lasers
Authors: Duling Irl N. , Dennis Michael L.
Published: February 2023

In an effort to utilize the full gain bandwidth of the erbium doped fiber for production of ultrashort pulses, several groups have used various methods of passive mode locking. This process is limited by the dispersion in the fiber cavity. Novel fibers are available which have very large normal dispersion at 1.5 microns. By adding small amounts of this fiber to the laser cavity the second order dispersion can be arbitrarily reduced. This type of compensation has allowed pulses shorter than 100 fs to be produced.[1]
Fibre Laser Source of Dual-Wavelength Femtosecond Pulses
Authors: Grudinin A.B. , Richardson D.J. , Abdulhalim I. , Pannell C.N. , Payne D.N.
Published: February 2023

Mode-locked erbium-doped fibre soliton lasers offer a range of desirable properties e.g. tunability and high pulse quality that make them suitable for applications in future nonlinear transmission and computation systems [1-3]. In particular, energy quantization effects caused by the soliton regime of operation of such lasers results in excellent individual pulse parameter stability with regard to pump power fluctuations. This feature is a result of the specific output of fibre soliton lasers, which consists of a number of soliton pulses and a non-soliton component. The output pulse parameters i.e. duration and energy are fixed by the cavity design. The number of circulating pulses is defined by the ratio of the average intracavity intensity to average soliton intensity. Generally this ratio is not an integer, causing the formation of a non-soliton component which plays the role of an energy buffer. Any excess stored intracavity energy (caused, for example, by small fluctuations of pump power) leads to changes in the non-soliton component leaving the parameters of the solitons largely unaltered. This excellent pulse amplitude stability allows complex, amplitude-sensitive nonlinear processing to be investigated such as that reported here.
Generation of periodic arrays of dark spatial solitons in the regime of effective amplification
Authors: Mamyshev Pavel V. , Bosshard Christian , Stegeman George I.
Published: February 2023

The generation of dark spatial optical solitons is of current interest because of their potential application to devices such as writing of waveguide structures and beam scanning for optical interconnects [1-3]. For such applications, it is important to have clean solitons without nonsoliton components. Current soliton generation techniques lead also to radiation fields (noise) due to the difficulty in producing precisely the initial conditions for launching [3]. In this paper we show that dark spatial soliton arrays can be launched through the adiabatic evolution of a simple interference pattern. The blackness of the solitons can be easily governed by changing the mutual intensity of the two interfering beams.
Generation of quasi-continuous trains of dark soliton-like pulses.
Authors: Allen K. M. , Doran N.J. , Williams J.A.R.
Published: February 2023

We present some results from a numerical integration of the Non-linear Schrodinger Equation for the copropagation of two high power bright pulses in optical fibres. These results show the possibility of generating a high repetition rate quasi-continuous train of stable dark soliton like pulses with parameters experimentally realisable using modelocked Ti:Sapphire lasers.
Effects of Phase Distortions in Conjugating Media
Authors: Bashaw M. C. , Aharoni A. , Hesselink L.
Published: February 2023

Phase conjugated light waves reverse phase distortions in media with negligible absorption or for paraxial beam propagation [1]. We examine here a different case in which a volume conjugating medium is itself imperfect, possessing phase distortions and a conjugating efficiency dependent on grating spatial frequency. We show theoretically that for multiplexed signals, cross-talk-free phase-conjugation is obtained only for negligible spatial-frequency dispersion and a phase-conjugated reference or pump wave, and we present supporting experimental results.
Frequency Doubling of a Semiconductor Laser Using an Organic Crystal Optical Waveguide
Authors: Hayashi Hideki , Hidaka Takahiro , Nakatani Hiroyuki
Published: February 2023

Compact and reliable blue and/or green coherent light sources are required for high density optical data storage, color image processing, and optical measurements. However, semiconductor lasers themselves using wide band-gap semiconductors, e.g., ZnSe/ZnS, have not yet been oscillated by continuous current injection at room temperature.
Enhanced Nonresonant Degenerate Four Wave Mixing in Conjugated Linear Chains through Excited State Population
Authors: Rodenberger D.C. , Heflin J.R. , Garito A.F.
Published: February 2023

A new enhancement mechanism for nonlinear optical processes originating from real population of electronic excited states in conjugated linear chains has been presented in previous theoretical studies.1,2 Compared to the ground state,3,4 the calculated nonresonant third-order optical susceptibility γSn(-ω4; ω1, ω2, ω3) of linear chain molecules can be enhanced by orders of magnitude, or even change sign, when the first (S1) or second (S2) electronic excited state is optically pumped and then populated for times suitably long to perform nonresonant measurements of γSn(-ω4; ω1, –ω2, ω3) at frequencies different from the resonant pump frequency. In this study, we report the first experimental observation of excited state enhancement of the degenerate four wave mixing (DFWM) susceptibility γSn(-ω; ω, –ω, ω) of a conjugated linear chain, diphenylexatriene (DPH), when the first π-electron excited state is populated for nanosecond timescales and then probed nonresonantly through picosecond DFWM.