bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental demonstration of 10 GBit/s, 4.7 ps pulse transmission over 4300km in a low dispersion, loss compensating dispersion decreasing fibre
Authors: Richardson D.J. , Dong L. , Ellis A.D. , Widdowson T. , Pender W.A.
Published: February 2023

Continuous, dispersion varying fibres (DVFs) offer a wide range of potential applications for distributed linear/nonlinear pulse manipulation and control. With the development of simple fibre fabrication technology capable of manufacturing up to 40 km lengths of DVF considerable attention has focussed on their potential application as a transmission media in advanced soliton communication systems. As pointed out by Tajima [1] fibres with exponentially varying dispersion matched to follow the fibre loss can be used to eliminate the deleterious effects of the local imbalances in nonlinearity and dispersion that arise as a result of the pulse energy variation between amplifier spans in a conventional soliton transmission line. These localised imbalances restrict the bit-rates that can be used in single channel systems once the soliton period of the pulses approaches that of the amplifier spacing, and also give rise to serious inter-channel effects in soliton WDM systems [5]. Single pulse transmission experiments have recently been demonstrated illustrating loss compensation over single amplifiers spans using loss compensating dispersion decreasing fibre (LCDDF)[2,3]. These early results have been followed by multi amplifier-stage experiments, illustrating application to the periodically amplified case for short pulses in regimes not permitted by conventional average soliton dynamics [4]. However, error free pulse transmission for high bit-rate single channel data transmission was found to be limited by effects such as the soliton acoustic interaction and Gordon Haus jitter which are pronounced due to the high path average path dispersion of the available LCDDFs [4]. In order to obtain significantly better results, LCDDFs with correspondingly smaller absolute dispersion range variations need to be developed. (Note that the application of a discrete approximation to the desired exponential dispersion profile for enhanced soliton WDM transmission have also been demonstrated [5]). In this paper we present initial results on the development of low dispersion, LCDDFs and present the first experimental results on the use of these more gently tapered fibres in recirculating loop experiments. We show that the lower average dispersion reduces the strong deleterious effects observed in the earlier loop experiments and obtain error free, 10 GBit/s, 4.7ps pulse transmission over fibre lengths in excess of 4300km.
Enhanced power solitons in optical fibres with strong dispersion management
Authors: Smith N.J. , Doran N.J. , Blow K.J. , Knox F.M. , Forysiak W.
Published: February 2023

The study of propagation in optical fibres with non-uniform dispersion has recently become a key topic in long haul optical communications. By using combinations of fibres with opposite sign dispersions, it is possible to construct a system which has high local dispersion at any given point, but a low path-average dispersion. This procedure strongly modifies the nonlinear transmission properties of the system compared with one constructed from uniformly low dispersion fibre, because the efficiency with which nonlinear four wave mixing processes are phase matched is substantially reduced[1, 2].
Bandgap Engineering for the Control of Second Order Non-linearities in GaAs/AlGaAs Asymmetric Multiple Quantum Well Waveguides
Authors: Street M.W. , Whitbread N.D. , Hamilton C.J. , Vögele B. , Aitchison J.S. , Hutchings D.C. , Marsh J.H. , Kennedy G.T. , Sibbet W.
Published: February 2023

Second order non-linear optical effects in quasi-phase-matched structures have been the subject of much research activity in recent years. In particular, cascaded χ(2):χ(2) interactions can give rise to non-linear phase shifts which may be employed in an all-optical switch device [1]. Here we are concerned with a novel quasi-phase-matching scheme which relies on the fact that an asymmetric MQW waveguide has associated with it significant second-order susceptibility tensor components which are not present for a symmetric QW structure [2]. By periodically intermixing an asymmetric MQW waveguide along its length therefore, these second-order non-linearities can, in theory, be modulated to achieve domain-disordered quasi-phase-matching. In this paper we shall present experimental evidence to demonstrate the feasibility of realising such a device in GaAs/AlGaAs for operation at 1.55µm. Un-phase-matched second-harmonic conversion efficiencies have been observed for disordered and non-disordered waveguides which suggest that the nonlinearity associated with asymmetric QWs is significantly reduced by intermixing. Experimental results also indicate that the spatial resolution of the impurity-free vacancy diffusion (IFVD) QW intermixing process [3] used throughout this work is sufficient for first-order quasi-phase-matching of the second harmonic generation.
Second order nonlinearity in glass film waveguides
Authors: Horinouchi Suguru , Imai Hiroaki , Hirashima Hiroshi , Mito Keiichi , Sasaki Keisuke
Published: February 2023

To date a lot of work1 has been carried out to understand the mechanism of second order nonlinearity in glass materials, but it has not been fully elucidated yet. Myers et al., who first reported2 a permanent second order nonlinearity of a poled bulk fused silica glass, explained the origin3 by a simple ionic charge transport model in combination with bond reorientation. Our group demonstrated phase-matched second harmonic generation (SHG) in corona-poled glass film waveguides4,5. The waveguide structure is essential for the further applications in integrated optics. Nevertheless the study on the quadratic nonlinearity in glass waveguides has not attracted much attention. In this article studies on the second order nonlinearity in corona-poled Coming 7059 glass film waveguides are reported.
Walking Spatial Solitons in Nonlinear Quadratic Media
Authors: Torner Lluis , Mazilu Dumitru , Mihalache Dumitru
Published: February 2023

Both, spatial and temporal solitons (more properly, solitary waves) exist in bulk crystals and in optical waveguides made of nonlinear quadratic media [1]-[3]. Bright spatial solitons have been already observed in second harmonic generation experiments [4]-[5]. Families of stationary soliton solutions of the governing are known to exist under ideal conditions, namely when there is no walk-off betwen the interacting waves [2]-[3]. Temporal walk-off is due to different group velocities of the waves forming the soliton, while spatial beam walk-off is due to different propagation directions of energy and phase fronts in anisotropic media. Beam walk-off is always present in the experiments when birefringence-tuning phase-matching techniques are used. Numerical experiments indicate that solitonlike propagation occurs in the presence of walk-off [2], but physically relevant soliton solutions are not known at present.
Soliton-Interface Interaction via Quadratic Nonlinearities
Authors: Boardman A D , Xie K
Published: February 2023

In recent times the discussion of envelope solitons, or spatial solitons has been addressing the use of second-order nonlinearity, [1-4] so it is appropriate to consider a substantial range of applications. The influence of an interface between two χ(2) materials, close enough to each other to create a controllable perturbation, remains to be solved. This is, therefore, an interesting fundamental, theoretical, problem in its own right. This problem is very important and will lead to a number of new and exciting applications.
Nonlinear directional coupler for solitary waves formed by the quadratic nonlinearity
Authors: Karpierz Miroslaw A.
Published: February 2023

Recently, the great effort of nonlinear guided-wave phenomena research is focused on the cascaded second-order process which can produce relatively large intensity-dependent phase changes of the wave propagating in optical waveguides [1-7]. Among a variety of nonlinear effects, the cascaded second order nonlinearity can be a source of forming temporal or spatial solitons [3-7], The phase mismatched second harmonic generation (ω+ω) and difference frequency generation (2ω-ω) lead to effective intensity-dependent phase changes of the pulse at both frequencies. This allows to form the pair of solitary waves at fundamental frequency and second harmonics with amplitude envelopes not changed along the propagation.
Power Controlled Ultrafast Wavelength Shifting
Authors: Villeneuve A. , Aitchison J. S.
Published: February 2023

Future optical communication system will probably be a mixture of wavelength division multiplexing (WDM) and optical time domain multiplexing (OTDM). It was shown recently that AlGaAs used at photon energies below the half-band gap is capable of performing OTDM functions[1]. In an OTDM system, signals are alloted different time slots, while in a WDM system, more than one wavelength are used to carry the signals. Hence there is a need to have wavelength shifting components to route signals. Furthermore, if OTDM and WDM are combined, the wavelength shifting will have to be ultrafast.
Soliton dynamics with fixed and sliding filters
Authors: Mecozzi Antonio
Published: February 2023

Inline frequency filtering [1, 2] is a powerful method to extend the limits imposed to soliton transmission by the Gordon-Haus jitter [3] and by the intensity noise of the amplifiers [4]. The use of filters gives many advantages. One is the increase of the bitrate distance product, otherwise limited for pulses of high intensity by the Gordon-Haus effect and for pulses of low intensity by the amplitude noise induced on solitons by the amplified spontaneous emission noise. The window of permitted soliton energies is without filters about 3 dB for 2.5 Gbit transmission over transoceanic distances [4]. With filters, the window significantly opens [5]. Filters of arbitrary strength cannot however be used. It was predicted in Ref. [1] that the strength of filters is limited by the growth of continuous wave radiation close to the filter center frequency. An elegant way to overcome this problem is to move with distance the filter center frequency. The transmission line becomes transparent to the signal and opaque to the noise [6]. Unfortunately, the sliding action has undesired effects on soliton propagation. The solitons with larger bandwidth are trapped more efficient by the filters. This means that the offset of the soliton center frequency from the filter center frequency is larger for solitons having smaller bandwidth, and consequently smaller energy. This converts intensity fluctuations into frequency fluctuations producing, ultimately, timing jitter [7]. This is the reason for the Gordon-Haus jitter observed in the experiment of Mollenauer et al. [8] being twice the value predicted by the Gordon-Haus theory, corrected to include the action of fixed filters. If intensity fluctuations convert into frequency fluctuations, also frequency fluctuations produce intensity fluctuations because of the frequency dependent loss of the filters. This cross coupling is the physical reason for the existence of a maximum allowed sliding rate. Beyond a critical value, the positive feedback established between a proper combination of intensity and frequency fluctuations becomes unstable [6, 7]. The maximum sliding rate is proportional to the cube of the soliton energy. Consequently, for a given value of sliding rate, there is a minimum value of soliton energy for stability. Besides a minimum, there is also a maximum for the allowed soliton energies because, for increasing soliton energy hence for increasing bandwidth, larger excess gain of the amplifier is required to overcome the filter loss. For soliton energy exceeding this maximum, the sliding rate is not sufficient to sweep away the amplified spontaneous emission noise at the filter center frequency and the soliton becomes unstable. This limits the window of the allowed energies to 3 dB for an optimized line at 10 Gbit/s [9].
All-optical steering of spatial solitary-waves through cascading in KTP
Authors: Assanto G. , Leo G. , Torruellas W. E. , Lawrence B. L. , Fuerst R. A , Stegeman G. I.
Published: February 2023

Solitary-waves of the quadratic nonlinearity have been recently revisited due to the renewed interest in coherent effects via second-order cascading [1-3] and the experimental observations of spatially confined field distributions in bulk KTP crystals. [4-5] Most investigations, however, have dealt primarily with such waves in the framework of scalar interactions between fields at the involved frequencies. [6-9] In this Communication we report on the angular steering of solitary waves formed in 2+1 dimensions through a vectorial or Type II Second Harmonic Generation (SHG) process in a bulk crystal of KTP. Steering was already observed with similar soliton-like waves in KTP by injecting a coherent SH seed of specified input phase.[5] On the contrary, we are able to control the beam lateral displacement after propagation by acting upon the relative intensities of two orthogonally-polarized input fields at the fundamental frequency (FF), i.e. without resorting to a phase controlled input at the second harmonic. Such an approach to phase-insensitive steering of two-dimensional solitary waves allows the implementation of reconfigurable interconnects through an input intensity imbalance at the (fundamental) frequency of relevance, eliminating the need for an additional (coherent) signal at the SH.
Efficient soliton compression by rapidly increasing amplification
Authors: Teixeiro M. Quiroga , Anderson D. , Andrekson P. , Berntson A. , Lisak M.
Published: February 2023

Access to soliton pulses of short pulse duration is an important prerequisite in many applications of solitons for optical fibre communication purposes. A number of methods for compressing solitons in optical fibers without generating nonsolitonic radiation modes has been suggested, e.g. adiabatic soliton compression by slow amplification [1] or by slowly decreasing dispersion [2]. In the present work we show that a properly tailored and rapidly increasing gain in an optical fiber can provide a fast, but still adiabatic, soliton amplification and concomitant efficient soliton compression for fiber lengths even shorter than the characteristic dispersion length. Using the variational approach, [3], explicit expressions are given for the required variation of the inhomogeneous gain and the resulting pulse compression. The validity of the analytical predictions are verified by comparison with numerical simulations of the pulse dynamics.
Collapse and Splitting of Dark Solitons
Authors: Afanasjev Vsevolod V. , Kivshar Yuri S.
Published: February 2023

Dark spatial solitons in nonlinear planar waveguides are observed as intensity dips on a broad (cw) background beam that do not diffract as the beam propagates [1]. These stationary nonlinearity-supported structures can be used as self-induced optical waveguides to guide or steer another (probe) beam, thus manipulating light by light. Recent experimental observations of dark spatial solitons [2-5] emphasize again the importance of dark solitons for all-optical applications.
Waveguide Methods for Measurements of Nonresonant Third Order Nonlinearities in Polymers
Authors: Gabler Th. , Bartuch U. , Waldhäusl R. , Peschel U. , Bräuer A. , Hörhold H.-H.
Published: February 2023

Besides semiconductor materials and semiconductor-doped glasses, conjugated polymers are one of the promising candidates for the realisation of opto-optical switching-concepts based on nonresonant third order nonlinearities [1, 2, 3]. Polymeric materials offer many advantages in comparison to other materials including ease of device fabrication and tailoring their linear and nonlinear behavior by chemical synthesis. Thus, there is an almost infinite number of different structures. Therefore it is very important to have different methods to measure the nonlinear refractive index in polymer waveguides. Simple and quick methods to get a fast view about sign and magnitude and more complex methods to get a value as accurate as possible to be able to design nonlinear waveguide elements like nonlinear direction coupler, phase modulator, beamscanner or grating coupler. We realized different experimental set-ups for these measurements based on an Argon-pumped Ti-Sapphire laser working in the ps- and in the fs-regime.
Vector spatial solitons
Authors: Aitchison J. S. , Hutchings D. C. , Kang J. U. , Stegeman G. I. , Ostrovskaya E. A. , Akhmediev N. N.
Published: February 2023

Spatial optical solitons have been receiving an increasing amount of attention due to their potential application for all-optical interconnects. Bright spatial solitons arise as a consequence of the balancing of self-focusing and diffraction in one transverse dimension. The half band gap nonlinearity in AlGaAs make this system ideal for the study of spatial solitons [1,2]
Competing nonlinearities at the origin of temporal soliton formation in a femtosecond OPO
Authors: Torruellas William E. , Jian Pey-Shuan , Peschel Ulf , Etrish Cristoph , Lederer Falk , Trillo Stefano , Haelterman Marc
Published: February 2023

While quadratic solitons had been predicted to exist theoretically and have been observed recently in planar waveguides and bulk quadratic crystals,[1-3] temporal soliton formation, or compensation for the refractive index dispersion by the quadratic nonlinearity, is difficult to be achieved in single path configurations because of the lack of materials with large enough dispersion. In other words, while the nonlinearities can afford parametric gain and phase front distortions, dispersion lengths are in the best case scenarios in the order of 10 cm which are difficult to be achieved experimentally with currently known quadratic materials.[4]
Stable multiple pulses in optical fibers with phase-sensitive amplification
Authors: Moore R. O. , Kath W. L. , Sandstede B. , Jones C. K. R. T. , Alexander J. C.
Published: February 2023

Using phase-sensitive parametric amplifiers (PSAs) has been suggested as a method for compensating loss in optical fibers.1 Because PSAs add no spontaneous emission noise to a propagating signal, they lead to a theoretically higher bit-rate-distance product in comparison with erbium-doped fiber amplifiers (EDFAs).2 Furthermore, PSAs stabilize pulse propagation because they eliminate phase variations across the pulse’s profile, thus strongly attenuating dispersion and self-phase modulation.3-5 Note that when PSAs are employed both the zero solution and a non-zero pulse solution are asymptotically stable. This bistable behavior, of course, is particularly desirable in digital optical communication and storage systems.6
Pulse-pulse interaction in systems with gain and loss
Authors: Akhmediev N. N. , Ankiewicz A. , Soto-Crespo J. M.
Published: February 2023

The emergence of stable spatio-temporal patterns in a variety of physical situations may be modeled through the well-known complex Ginzburg-Landau equation (CGLE). In optics, it is useful in analyzing optical transmission lines [1, 2, 3, 4] and fiber lasers [5, 7, 8, 9, 10, 11]. In each case, the problem of the interaction of two neighboring pulses is crucial for transmission of information [12].
The effect of pump fluctuation in supercontinuum pulse generation
Authors: Mori Kunihiko , Takara Hidehiko , Kawanishi Satoki
Published: February 2023

It is important to clarify the noise characteristics in a supercontinuum (SC) pulse source for its application to high-capacity optical communications[1]-[3]. Morioka et al have measured bit-error rates (BER) [4] and timing jitters[5] in filtered SC pulses and showed that the SC pulses have BER and jitter characteristics almost equal to those of the pump pulses. Recently, we have successfully performed numerical simulations of SC generation[6] and had a good agreement with the previous experiment [4]. Since the simulation model is based on classical beam propagation in a nonlinear medium with no stochastic processes, the noise characteristics in SC generation should be from deterministic processes such as fluctuation in the pump pulses and not from stochastic processes such as background spontaneous emission. On the analogy of many nonlinear phenomena, it is predicted that slight fluctuation in pump pulses is inherited by generated SC pulses with amplification.
Two-dimensional quadratic solitons collision in KTP
Authors: De Angelis C. , Costantini B. , Bourliaguet B. , Kermene V. , Barthelemy A.
Published: February 2023

In the past ten years it was proved both theoretically and experimentally that cubic spatial solitons can be exploited to achieve fast all-optical processing of optical data. Taking benefit of the quasi-instantaneous response of Kerr type nonlinearity transient waveguides were generated by spatial solitons into homogeneous nonlinear materials[1]. It was also possible to modify at ultrafast speed the geometry of the waveguides thanks to the various interactions that may occur between soliton beams: couplers for signal splitting or combining and switches were realized using parallel solitons coupling [2] or solitons collision and fusion [3]. Spatial soliton based optical processing look attractive for routing high data rate streams. In the case of Kerr type nonlinearity however, the envisaged devices need a planar waveguide structure to avoid two-dimensional transverse instability and the peak powers required to reach self-guiding are close to 1 kW, even with the use of material of high nonlinearity. It was recently shown theoretically first and then experimentaly [4] that spatial solitary waves propagation can take place also in crystals exhibiting a substantial quadratic nonlinearity. This opened up new hopes on the use of soliton in optical processing. It was demonstrated that quadratic spatial solitary waves (QSSW) are stable even in the case of bulk propagation (2D-QSSW) on the contrary to their cubic counterparts. Moreover the advent of new materials, some of them of organic type, with high nonlinear coefficient lets expect that the self-guiding power threshold could be decreased below the above mentionned value for cubic spatial solitons. As it happened for interactions and collisions between kerr-type solitons, those between QSSWs are expected to offer the same promising field of applications. The problem of QSSWs collisions has been in fact recently addressed; as long as one refers to type I interactions, the problem has been treated numerically for both the 1D and 2D cases [5], analytically and experimentally only for the 1D case [6]. On the other hand, if type II (or vectorial) processes are concerned, the problem of QSSWs interactions has been faced only numerically or analytically both in the 1D and 2D cases [7].
Quasi-phase-matching by periodic modulation of nonlinear optical coefficients in semiconductor waveguides
Authors: Hutchings D.C. , Street M.W. , Whitbread N. , Aitchison J.S. , Marsh J.H. , Arnold J.M.
Published: February 2023

To obtain quasi-phase-matching it is sufficient merely to achieve a periodic modulation of the nonlinear coefficient, particularly if the nonlinear coefficient itself is large. We address two methods of implementing this in semiconductors using quantum well disordering: modulation of an induced nonlinearity (e.g., asymmetric heterostructure) and modulation of a bulk-like nonlinearity by blue-shift of the band-edge.
Cascadable rms characteristics and average dynamic of pulses in dispersive nonlinear lossy fibers
Authors: Bélanger Nicolas , Bélanger Pierre-André
Published: February 2023

More accurate equations describing the propagation law of the three rms parameters in average- soliton regime are presented. These equations are cascadable from a piece of fiber to another making them useful for designing dispersion maps. Finally, the average soliton dynamic is generalized to any pulse shape even if the hyperbolic secant seems to be the optimal case.
Average dark soliton dynamics in periodically dispersion compensated fiber transmission systems
Authors: Chen Yijiang , Atai Javid
Published: February 2023

We examine propagation of dark solitons in periodically dispersion compensated (PDC) fiber transmission systems. Distinctive features of the dark soliton in PDC transmission systems are reported and are compared with the bright soliton.
Gain characteristics in birefringent fiber optical parametric amplifiers
Authors: Sylvestre T. , Maillotte H. , Lantz E.
Published: February 2023

With the advent of high peak power integrated laser sources, optical parametric amplification (OPA) can be useful for signal amplification and noise reduction in fiber systems. OPA is induced by mixing a strong pump wave and a signal wave of different frequency in a Kerr medium. The temporal intensity modulation resulting from the beating of the two waves creates a moving index grating via the optical Kerr effect1. It leads to modulation instability in the temporal domain and to the growth of spectral sidebands around the pump frequency, the so-called four wave-mixing spectrum. As the involved waves experience different group-velocities because of material and modal dispersions and intensity-dependent nonlinear phase shifts, a phase-matching condition is necessary to ensure exponential-like growth of the amplification. Many studies have focused on the theory of parametric amplification in fibers. They led to show the formal equivalence of modulation instability (MI) and four-wave mixing (FWM).2,3
Stability criterion and multistability of Kerr-like gap solitons
Authors: De Rossi Alfredo , Conti Claudio , Trillo Stefano
Published: February 2023

It is well-known that periodic Bragg structures induce gaps in the linear dispersion relation where the propagation is forbidden. Thanks to the nonlinearity, the e.m. energy can be localized at these frequencies in the form of gap solitons [1-5]. Their most intriguiging feature is the possibility to travel with velocities much slower than the light velocity, or remarkably even at zero velocity (stationary trapping) in the limit case. Propagation of slow solitonic envelopes was recently demonstrated experimentally operating near Bragg wavelength of a fiber grating [5]. However no experimental data in the region of zero (or extremely small) velocities has been reported to date. To address the observability of stationary localization, a fundamental prerequesite to be fullfilled is the stability of the gap solitons. In spite of its importance the stability problem for gap solitons was left practically unaddressed, except for few numerical simulations. Here our purpose is to derive an analytical stability criterion, starting from the usual coupled-mode formulation of the propagation [1]. This involves derivatives of the invariants similarly to a well-known criterion for equations with second-order dispersion (i.e., nonlinear Schrödinger type [6]), recently extended to quadratic solitons [7,8]. Specifically, we consider the Lorentz-invariant Hamiltonian equations which rule the propagation of forward (+) and backward (−) envelopes u
±
at Bragg or gap-center carrier frequency with cubic nonlinearity [1,2] where H is the conserved Hamiltonian of Eqs. (1).
Generation and propagation of stable periodic arrays of soliton stripes in a bulk Kerr liquid
Authors: Maillotte Hervé , Grasser Régis
Published: February 2023

Stable periodic arrays of Kerr soliton stripes are generated within bulk carbon disulfide and propagate through the medium by controlling modulation instability with Bragg diffraction.
Controlling Chaos in a Simple Nonlinear Fibre Resonator
Authors: Lynch S. , Steele A.L.
Published: February 2023

In 1979, Ikeda [1] showed that an optical resonator containing a nonlinear optical element could not only have a bistable behaviour, but the system could also go unstable at certain power levels. Nonlinear optical fibre resonators can exhibit these Ikeda instabilities as well as the bistable behaviour [2-4]. Obviously, an unstable output is unwanted in a bistable device and methods need to be investigated to limit or remove the chaotic behaviour. One possible solution is to use a method for stabilizing unstable periodic points on the chaotic attractor by applying small perturbations of a control parameter, first proposed by Ott, Grebogi and Yorke (OGY) in 1990 [5], who stabilized an unstable point in the Hénon map, even in the presence of noise. We report here on the application of the OGY method to the Ikeda map, which can be shown to describe the iterative passage of the electric field around a simple nonlinear fibre resonator, see Fig. 1, [4]. The focus is on the fundamental possibility of controlling the Ikeda instabilities and not on the practicalities, which may be challenging.
Raman-effect-based optical switching in highly GeO2-doped fibers
Authors: Starodumov A.N. , Barmenkov Yu.O. , Martinez A. , Torres I.
Published: February 2023

All-optical switching have attracted much interest in recent years as an alternative to electronic switching in optical communication systems. A number of devices based on a Sagnac fiber interferometer, known also as the nonlinear loop mirror (NOLM), have been proposed for ultrafast switching [1-6]. A standard NOLM uses cross-phase modulation between co-propagating control and signal pulses to switch a signal pulse from one arm to the other. An ultrafast nonlinear response in fiber is generated through the optical Kerr effect. A noninterferometric device, which could join switching and amplification functions, would be very prospective for signal processing. Stimulated Raman scattering (SRS) may be considered as a potential mechanism for ultrafast switching and amplification because of its femtosecond response time. A common point of view is that the main drawback of SRS in fibers is its relatively high pump power requirements. Here we describe and demonstrate new Raman effect-based optical switch, which joins switching and amplification functions. We show that the control pulse power requirements for the Raman switch are expected to be practically the same as for the Kerr switch.
Phase-locking and periodic evolution of solitons in passively mode-locked fiber lasers with slow saturable absorber
Authors: Soto-Crespo J. M. , Akhmediev Nail
Published: February 2023

Passively mode-locked fiber lasers [1-6] are a unique source of solitons for telecommunications. Ultra-short pulse generation in laser systems is based on a variety of schemes including figure of eight fiber laser design [1], fast saturable absorber [3], coupled cavity [5], additive pulse mode-locking [6] and nonlinear polarization rotation [7,8]. The use of a semiconductor mirror-saturable absorber has been suggested for a passively mode-locked soliton laser [9] and its experimental verification has been reported in [10].
All-optical buffers via localization of two-color quadratic gap solitons
Authors: Assanto Gaetano , Conti Claudio , Trillo Stefano
Published: February 2023

Optical gap solitons are a promising approach towards the realization of all-optical buffers and memories in nonlinear waveguides with Bragg resonant gratings [1]. In fact they permit to localize the e.m. energy at zero-velocity in the laboratory frame, in a frequency range where the linear propagation is otherwise forbidden. A recent experiment on slowly-traveling localized states has been reported by Eggleton et al. in an index-modulated fiber through the Kerr effect [2]. However, the trapping of zero velocity solitons within the grating is still an open issue, despite the fact that perfectly steady gap solitons could become the basic elements in all-optical memories. More recently, in the context of parametric quadratic effects, structures with distributed-feedback gratings (DFBG), Bragg-coupled to one or both frequencies in media for Second-Harmonic Generation (SH G), have been shown to support two-color gap solitons, i.e. localized energy states of trapped field components at the fundamental (FF) and its second harmonic (SH), based on the interplay of grating dispersion, parametric gain and cascading phase shifts [3-7]. In this Communication we numerically demonstrate that stationary gap simultons can be excited in a quadratically nonlinear DBFG via inelastic scattering of pulses launched at the FF, and can be detected using a similar ”reading” beam.
Analysis of stabilizing effect of filters in dispersion-managed soliton systems
Authors: Matsumoto Masayuki
Published: February 2023

Recent studies of dispersion-managed solitons show that their pulse energy in the steady state is larger than that of the conventional soliton with the same (minimum) pulse width and the same (averaged) fiber dispersion [1]. The enhanced pulse energy reduces the relative effect of noise emitted from inline optical amplifiers, which can extend the transmission distance. This indicates that the use of control schemes such as frequency-sliding filters and synchronous modulation may not be needed in the dispersion-managed soliton systems [2]. The use of filters with appropriate bandwidth, however, can be beneficial to increase further the system length [3]. The filters may also be effective to reduce mutual interaction between adjacent pulses that is one of the factors limiting the performance of dispersion-managed solitons with strong power enhancement. The author previously carried out a semi-numerical analysis of the effect of filters on the dispersion-managed soliton (stretched pulse) transmission [4]. In this paper analytical expressions for the strength of stabilizing pulse energy and frequency by the filters are given.
Third harmonic generation of Nd:YAG laser light in periodically poled LiNbO3 waveguide
Authors: Kintaka K. , Fujimura M. , Suhara T. , Nishihara H.
Published: February 2023

Third harmonic generation (THG) is one of the most attractive techniques for producing short-wavelength coherent light. THG is yielded by a third-order nonlinear process, but it is difficult to achieve efficient THG because the third-order nonlinear optical coefficient is usually small. A TH wave can also be obtained by using two second-order nonlinear processes in series, and high efficiency can be expected because second-order nonlinear processes are usually more efficient than third-order nonlinear processes. In this method, a pump wave is once converted into a second harmonic (SH) wave, and then converted into a TH wave by frequency-mixing of the pump wave and the generated SH wave. Previous works used two bulk crystals and a birefringent phase-matching method for such second-order nonlinear processes [1]. Recently, efficient second-order nonlinear processes have been demonstrated by using a waveguide structure and ferroelectric-domain-inverted grating for quasi-phase-matching (QPM) in second harmonic generation (SHG) devices [2-8] and sum-frequency generation (SFG) devices [9]. We have proposed the application of such techniques to the generation of a TH wave [10]. In this paper, we demonstrate THG of a Nd:YAG laser light with cascading QPM-SHG and QPM-SFG in LiNbO3 waveguide.
Self-focusing and solitary waves in bulk media with χ(2) and χ(3) nonlinearity
Authors: Bang Ole , Kivshar Yuri S. , Buryak Alexander V. , De Rossi Alfredo , Trillo Stefano
Published: February 2023

The basic theory of two-wave parametric solitons in materials with a pure quadratic (or χ(2)) nonlinearity is now well understood, and importantly, many of the results have been confirmed experimentally [1]. In particular, in bulk media, families of stable spatial solitons exist above a certain threshold power [2]. Their excitation from input Gaussian beams has been confirmed both numerically [3] and experimentally [4]. In fact self-focusing, leading to a catastrophic collapse, cannot occur in χ(2) media [5].
Higher-order quasi-solitons of an adapted dispersion profile
Authors: Paré C.
Published: February 2023

Some years ago, Tajima [1] suggested that the solitonic balance between nonlinearity and dispersion could be maintained in a lossy fiber by a proper (exponential) tailoring of the dispersion profile. Since then, the idea has been generalized to include higher-order effects [2]. More recently, Kumar and Hasegawa [3] introduced the concept of " quasi-soliton ", a chirped soliton adapted to a novel dispersion profile. The pre-chirping of the input soliton has the advantage of limiting the emission of radiation and reducing the pulse interaction [4]. In this paper, we discuss of the existence of higher-order quasi-solitons that can propagate along the same dispersion profile with the same evolution of their parameters. Analytical expressions are presented for the pulse shapes, as well as the appropriate grating parameter required for long-haul transmission.
Periodically conjugated solitons in dispersion-managed optical fiber
Authors: Piña Jaime , Abueva Bryan , Goedde Christopher G. , Kath William L.
Published: February 2023

Optical phase conjugation (OPC) and dispersion management are both techniques for improving high-speed optical communication systems using very short (width < 10 ps) solitons. OPC can be used at either the fiber mid-point [1, 2] or periodically [3, 4] to reduce Gordon-Haus jitter and soliton-soliton interactions. Similarly, dispersion management can be used to reduce jitter as well as the effects of soliton collisions in WDM systems [5, 6].
Frequency-resolved optical gating at 1.5 μm using the Kerr nonlinearity in optical fibres
Authors: Thomson M. D. , Dudley J. M. , Barry L. P. , Harvey J. D.
Published: February 2023

Frequency-resolved optical gating (FROG) is rapidly becoming a routine measurement technique for the characterisation of ultrashort light pulses, and a number of different experimental schemes based on nonlinear processes in bulk materials have been demonstrated [1]. As the use of FROG becomes more widespread, there will be increasing demand for additional convenient geometries for particular experimental applications. In this paper, we use the Kerr nonlinearity in 20 m of dispersion-shifted fibre as the nonlinear process for a novel Fibre-FROG geometry, and characterise the intensity and phase of picosecond pulses around 1.5 μm. The results are found to be in excellent agreement with results obtained using a standard second-harmonic generation (SHG) FROG technique.
Reconfigurable multichannel amplitude equalizer based on cascaded silicon photonic microrings
Authors: Zhang Changping , Liu Shujun , Yan Hao , Liu Dajian , Zhang Long , Li Huan , Shi Yaocheng , Liu Liu , Dai Daoxin
Published: February 2023

A compact on-chip reconfigurable multichannel amplitude equalizer based on cascaded elliptical microrings is proposed and demonstrated experimentally. With the optimized structure of the elliptical microring with adiabatically varied radii/widths, the average excess loss for each channel in the initialized state is measured to be less than 0.5 dB, while the attenuation dynamic range can be over 20 dB. Flexible tunability through the overlapping of the resonance peaks of adjacent wavelength-channels enables even higher attenuation dynamic ranges up to 50 dB. Leveraging the thermo-optic effect and fine wavelength-tuning linearity, precise tuning of the resonance peak can be implemented, enabling dynamic power equalization of each wavelength-channel in wavelength-division-multiplexing (WDM) systems and optical frequency combs. The proposed architecture exhibits excellent scalability, which can facilitate the development of long-haul optical transport networks and high-capacity neuromorphic computing systems, while improving the overall performance of optical signals in WDM-related systems.
Numerical simulations of the soliton dynamics for a nonlinear biological model: Modulation instability analysis
Authors: Vivas-Cortez Miguel , Arshed Saima , Sadaf Maasoomah , Perveen Zahida , Akram Ghazala
Published: February 2023

This article deals with studying the dynamical behavior of the DNA model proposed by Peyrard and Bishop. The proposed model is investigated using the unified method (UM). Unified method successfully extracts solutions in the form of polynomial and rational functions. The solitary wave solutions and soliton solutions are constructed. An investigation of modulation instability is also presented in this paper. 3D and 2D plots are presented to exhibit the physical behavior of some of the obtained solutions.
Gadolinium-enhanced MRI visualizing backflow at increasing intra-renal pressure in a porcine model
Authors: Lildal Søren Kissow , Hansen Esben Søvsø Szocska , Laustsen Christoffer , Nørregaard Rikke , Bertelsen Lotte Bonde , Madsen Kirsten , Rasmussen Camilla W. , Osther Palle Jörn Sloth , Jung Helene
Published: February 2023

Introduction

Intrarenal backflow (IRB) is known to occur at increased intrarenal pressure (IRP). Irrigation during ureteroscopy increases IRP. Complications such as sepsis is more frequent after prolonged high-pressure ureteroscopy. We evaluated a new method to document and visualize intrarenal backflow as a function of IRP and time in a pig model.

Methods

Studies were performed on five female pigs. A ureteral catheter was placed in the renal pelvis and connected to a Gadolinium/ saline solution 3 ml/L for irrigation. An occlusion balloon-catheter was left inflated at the uretero-pelvic junction and connected to a pressure monitor. Irrigation was successively regulated to maintain steady IRP levels at 10, 20, 30, 40 and 50 mmHg. MRI of the kidneys was performed at 5-minute intervals. PCR and immunoassay analyses were executed on the harvested kidneys to detect potential changes in inflammatory markers.

Results

MRI showed backflow of Gadolinium into the kidney cortex in all cases. The mean time to first visual damage was 15 minutes and the mean registered pressure at first visual damage was 21 mmHg. On the final MRI the mean percentage of IRB affected kidney was 66% after irrigation with a mean maximum pressure of 43 mmHg for a mean duration of 70 minutes. Immunoassay analyses showed increased MCP-1 mRNA expression in the treated kidneys compared to contralateral control kidneys.

Conclusions

Gadolinium enhanced MRI provided detailed information about IRB that has not previously been documented. IRB occurs at even very low pressures, and these findings are in conflict with the general consensus that keeping IRP below 30–35 mmHg eliminates the risk of post-operative infection and sepsis. Moreover, the level of IRB was documented to be a function of both IRP and time. The results of this study emphasize the importance of keeping IRP and OR time low during ureteroscopy.
Joint modeling of longitudinal changes of blood pressure and time to remission of hypertensive patients receiving treatment: Bayesian approach
Authors: Getaneh Frezer Tilahun , Tesfaw Lijalem Melie , Dessie Zelalem G. , Derebe Muluwerk Ayele
Published: February 2023

Introduction

Hypertension is a widespread condition when the blood’s force on the artery walls is extremely high to develop adverse health effects. This paper aimed to jointly model the longitudinal change of blood pressures (systolic and diastolic) and time to the first remission of hypertensive outpatients receiving treatment.

Methods

A retrospective study design was used to collect appropriate data on longitudinal changes in blood pressure and time-to-event from the medical charts of 301 hypertensive outpatients under follow-up at Felege Hiwot referral hospital, Ethiopia. The data exploration was done using summary statistics measures, individual profile plots, Kaplan-Meier plots, and log-rank tests. To get wide-ranging information about the progression, joint multivariate models were employed.

Results

A total of 301 hypertensive patients who take treatment was taken from Felege Hiwot referral hospital recorded between Sep. 2018 to Feb. 2021. Of this 153 (50.8%) were male, and 124 (49.2%) were residents from rural areas. About 83(27.6%), 58 (19.3%), 82 (27.2%), and 25 (8.3%) have a history of diabetes mellitus, cardiovascular disease, stroke, and HIV respectively. The median time of hypertensive patients to have first remission time was 11 months. The hazard of the patient’s first remission time for males was 0.63 times less likely than the hazard for females. The time to attain the first remission for patients who had a history of diabetes mellitus was 46% lower than for those who had no history of diabetes mellitus.

Conclusion

Blood pressure dynamics significantly affect the time to the first remission of hypertensive outpatients receiving treatment. The patients who had a good follow-up, lower BUN, lower serum calcium, lower serum sodium, lower hemoglobin, and take the treatment enalapril showed an opportunity in decreasing their blood pressure. This compels patients to experience the first remission early. Besides, age, patient’s history of diabetes, patient’s history of cardiovascular disease, and treatment type were the joint determinant factors for the longitudinal change of BP and the first remission time. The Bayesian joint model approach provides specific dynamic predictions, wide-ranging information about the disease transitions, and better knowledge of disease etiology.
A systematic review of the barriers, enablers and strategies to embedding translational research within the public hospital system focusing on nursing and allied health professions
Authors: Smith Sophie , Johnson George
Published: February 2023

Aim

This systematic review aims to investigate, identify, and compare evidence related to the barriers, enablers, and strategies to embedding translational research within a public hospital system focussed on nursing and allied health disciplines.

Methods

A systematic review looking at the international literature on the barriers, enablers and strategies in embedding translational research within a public health system addressing nursing and allied health professions. The study channelled the PRISMA reporting guidelines for systematic reviews and meta-analyses. Databases searched were Medline, Embase, Scopus and Pubmed from January 2011 to December 2021 (inclusive). A quality assessment was conducted of literature using the mixed methods appraisal tool 2011 version.

Results

Thirteen papers met the inclusion criteria. The studies included were from Australia, Saudi Arabia, China, Denmark and Canada. Occupational therapy and physiotherapy were the only two allied health disciplines identified in the search process. The review found considerable inter-relationships between the enablers, barriers, and strategies to embedding research translation in a public hospital setting. Three over-arching themes ‘leadership, organisational culture and capabilities’ were developed to capture the complexity of factors in embedding translational research. Key subthemes identified were education, knowledge, management, time, workplace culture and resources. All thirteen articles identified that a multifactorial approach is required to embed a research culture and translate research findings into clinical practice.

Conclusions

The themes of leadership, organisational culture and capabilities are inherently intertwined and therefore successful strategies require a whole of health approach with organisational leadership driving the strategy, as changing organisational culture takes time and considerable investment. We recommend that public health organisations, senior executives and policy makers consider the findings of this review to provide evidence to initiate organisational changes to support and help create a research environment to drive research translation within the public sector.