Spatial Solitons in Random Quadratic Media

Evolution of spatial solitons in quadratic media with fluctuating nonlinearity

This work analyzes the dynamics of two-dimensional spatial solitons in dissipative graded index Kerr media, analytically and numerically. The dynamics of two-dimensional spatial solitons has been studied in a medium with lumped amplification. The presence of lumped amplification in the medium results in the formation of soliton like waves called similaritons. The spatial soliton dynamics has been studied in a dissipative medium. In a dissipative graded index Kerr medium, the balancing between the coefficients of constant dissipation and lumped amplification results in the stabilization of the beam. The beam dynamics has also been studied by varying amplification coefficients with propagation distance. Hyperbolic, linear, and exponential amplification profiles are considered. When amplification coefficient varies with propagation distance, the beam gets compressed. The beam compression is higher in the case of exponential amplification profile than that of hyperbolic and linear amplification profiles.

Optical pulse propagation in fibers with random dispersion

Recently there has been much interest in designing optical tapers for nonlinear pulse manipulation in both standard[1] and semiconductor filled fibres[2]. Such tapers can be used to overcome the large linear losses in semiconductor filled fibres while allowing parabolic pulse generation or soliton propagation for example. However once the taper profile has been chosen to overcome the linear loss problem in semiconductor filled fibres the problem of two photon absorption (TPA) and associated free carrier effects remain. In this work we show that it is possible to use a genetic algorithm to design tapers that alleviate both linear and nonlinear losses and hence should allow high quality pulse propagation over several centimetres of semiconductor filled fibres.

This paper addresses the problem of Bayesian wavelet estimating the mean vector of multivariate normal distribution under a multivariate normal prior distribution based on linear and nonlinear exponential balanced loss functions. The covariance matrix of multivariate normal distribution is considered known. Bayes estimators of mean vector parameter of multivariate normal distribution are achieved. Then two soft shrinkage wavelet threshold estimators based on Stein’s unbiased risk estimate (SURE) and Bayes estimators are provided. Finally, the performance of the soft shrinkage wavelet estimators was checked through simulation study and Electrical Grid Stability Simulated data set. Simulation and real data results showed the better performance of SURE thresholds based on linear and nonlinear exponential balanced loss functions compared to other classical wavelet methods. Also, they showed better performance for SURE threshold based on nonlinear exponential balanced loss function in multivariate normal distribution with small dimensions.

Spatiotemporal nonlinear effects caused by the interplay between transverse modulation and nonlinearity open the rich field of research on wave propagation in nonlinear structures. In optics, the induction of two-dimensional refractive index structures in photorefractive materials has been utilized to demonstrate for instance discrete solitons, Bloch oscillations and Zener tunneling, as well as discrete vortex solitons. The unique properties of photorefractive crystals like strontium barium niobate (SBN) facilitate highly nonlinear and reconfigurable refractive index patterns even at low power levels.

We report experiments on high-amplitude sound wave propagation in an acoustic metamaterial composed of an air-filled waveguide periodically side-loaded by holes. In addition to the linear viscothermal and radiation losses, high amplitude sound waves at the locations of the side holes introduce nonlinear losses. The latter result in an amplitude-dependent reflection, transmission, and absorption, which we experimentally characterize. First, we evidence that nonlinear losses change the nature of the device from a reflective to an absorbing one, showing the possibility to use the system as a nonlinear absorber. Second, we study the second-harmonic generation and its beating phenomenon both experimentally and analytically. We find that when considering the propagation of both the fundamental and the second harmonic, nonlinear losses cannot be neglected. Our results reveal the role of nonlinear losses in the proposed device and also provide a quite accurate analytical model to capture the effect of such losses.

Optical amplification in silicon photonic integrated circuits remains a challenge and stimulated Raman scattering has been proposed as a means of achieving optical gain in silicon. In this work, we experimentally investigate silicon Raman amplifiers optimized for fabrication with open-access foundry sub-micron silicon platform. We discuss and experimentally validate the importance of considering the non-reciprocal Raman-gain by using counter-propagating or co-propagating pumps and probes, different amplifier lengths, input pump powers and nonlinear loss values. We demonstrate a Raman-assisted loss-less optical circuit in a 1.2-cm-length waveguide that reaches zero net-gain with only 60 mW continuous-wave pumping. A 5.5 dB stimulated Raman scattering (SRS) gain yielding 0.5 dB net-gain is also demonstrated with a 115 mW pump in a 3.25-cm waveguide. Furthermore, we examine the nonlinear loss of silicon waveguides to estimate free carrier lifetime (FCL) with different bias voltages applied to the waveguide <i>p-i-n</i> structure. Accounting for non-reciprocal Raman amplification by using the two dataset of co- and counter-propagating SRS gain, we extract the Raman gain coefficient of this 220 nm thick silicon photonic waveguide. We perform the curve fitting over the whole input pump power range using the extracted FCL, and over the low power range where only linear loss is expected. We find a good agreement in the extracted Raman gain coefficients. We use these key parameters as input to a silicon photonic Raman amplifier model to find the optimum performance based on the available footprint and pump power.

The optimal physical conditions of single-longitudinal-mode (SLM) operation for continuous-wave all-solid-state lasers with high output powers are investigated theoretically and experimentally. The dependence of the operation conditions on the linear and nonlinear intracavity losses of the laser is numerically calculated. The theoretical analysis is demonstrated by the experimental measurements on a home-made Nd:YVO4 laser. The stable SLM output up to 33.7 W with optical-optical conversion efficiency of 44.9% at 1064 nm wavelength is recorded for over 7 h. The experimental results are in good agreement with the theoretical expectation.

We numerically demonstrate the feasibility of constructing an all-optical pulse restorer by using a microresonator structure with Kerr nonlinearity. We obtain a clear nonlinear power transfer curve suitable for all-optical regeneration (reshaping) in the frequency and the time domains. The fully integrated device is based on 2 cascaded sets of finite chains of 3 coupled nonlinear identical microring resonators side coupled with 3 straight waveguides. The microrings are constituted by the same instantaneous, dispersive, local Kerr material. The first set suppresses the noise in "0" and the second limits the amplitude fluctuations in "1" of return-to-zero optical data streams. For a device made in p-toluene sulphonate (PTS) with <i>n</i>₂ = 2.2&times;10^-12 cm²/W with linear losses &alpha; = -5 dB/cm and nonlinear losses &alpha;₂ = 0.5 cm/GW and considering amplitude, jitter and width fluctuations we evaluate an amplitude Q-factor improvement of 4.94 dB for a data rate of 40 Gb/s and input intensity n₂<i>I</i>₀ = 5 &times; 10^-4. Since we take advantage from field enhancement at resonance, this integrated reshaper could be much smaller than other gates based on nonlinear fibers or waveguides.

Organic materials that exhibit large real third-order optical nonlinearities, |Re(χ(3))|, and that also have low linear and nonlinear losses at telecommunication wavelengths may be useful for a range of all-optical signal-processing (AOSP) applications. Based on their solution linear and nonlinear optical characteristics, polymethine dyes in general, and chalcogenopyrylium-terminated heptamethines in particular, are a promising class of materials for AOSP, but the translation of their microscopic nonlinearity to device-relevant materials is hindered by significant aggregation of the molecules in high-chromophore density films.[1] An approach to minimize aggregation these dyes, in which bulky and rigidly out-of-plane groups are introduced both in the center of the polymethine bridge and on the heterocyclic end groups, has been developed and can lead to thin-film materials exhibiting combinations of large |Re(χ(3))|, large two-photon figure-of-merit, and low linear loss that are suitable for AOSP.[2] [1] Hales J. M., Matichak J., Barlow S., Ohira S., Yesudas K., Bredas J.-L., Perry J. W. and S. R. Marder, Science, 2010, 327, 1485. [2] Barlow S., Bredas J.-L., Getmanenko Y. A., Gieseking R. L., Hales J.M., Kim H., Marder S.R., Perry J. W., Risko C., Zhang Y., Materials Horizons, 2014, 1, 17.

A Korteweg–de Vries description of dark solitons in polariton superfluids

Nonlinear hydraulic coupling characteristics and energy conversion mechanism of pipeline - surge tank system of hydropower station with super long headrace tunnel

Ferroresonance is a complex electrical phenomenon, which can cause overvoltages in the electrical power system and endangers the system reliability and continuous safe operating. This paper studies the effect of linear and nonlinear core losses on the chaotic ferroresonance in a voltage transformer. For confirmation this aspect simulation has been done on a one phase voltage transformer rated 100VA, 275kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with q=7. The simulation results reveal that considering the nonlinear core losses on the voltage transformer, exhibits a great effect on ferroresonance overvoltages. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance voltages has been obtained and presented.

Broadband analog signal processors utilizing silicon photonics have demonstrated a significant impact in numerous application spaces, offering unprecedented bandwidths, dynamic range, and tunability. In the past decade, microwave photonic techniques have been applied to neuromorphic processing, resulting in the development of novel photonic neural network architectures. Neuromorphic photonic systems can enable machine learning capabilities at extreme bandwidths and speeds. Herein, low‐quality factor microring resonators are implemented to demonstrate broadband optical weighting. In addition, silicon photonic neural network architectures are critically evaluated, simulated, and optimized from a radio‐frequency performance perspective. This analysis highlights the linear front‐end of the photonic neural network, the effects of linear and nonlinear loss within silicon waveguides, and the impact of electrical preamplification.