Compression and stretching of ring vortex in a bulk nonlinear medium

We explore the nonlinear gain coupled Schrödinger system through the utilization of the variables separation method and ansatz technique.By employing these approaches,we generate hierarchies of explicit dissipative vector vortices(DVVs)that possess diverse vorticity values.Numerous fundamental characteristics of the DVVs are examined,encompassing amplitude profiles,energy fluxes,parameter effects,as well as linear and dynamic stability.

Topological laser on square lattice with gain–loss-induced higher-order corner modes

We investigate the higher-order topological laser in the two-dimensional(2D) coupled-cavity array. By adding staggered on-site gain and loss to the 2D Hermitian array with a trivial phase, the system will emerge degenerate topological corner modes, which are protected by bulk band gap. For such a non-Hermitian model, by adjusting the parameters of the system and introducing the pumping into the cavity at the corner, a single-mode lasing with topological protection emerges.Furthermore, single-mode lasing exists over a wide range of pumping strengths. No matter where the cavity is initially stimulated, after enough time evolution, all the cavities belonging to the topological corner mode can emit a stable laser.

ALMOST DISTURBANCE DECOUPLING FOR A CLASS OF MINIMUM-PHASE HIGHER-ORDER CASCADE NONLINEAR SYSTEMS

The problem of almost disturbance decoupling (ADD) with internal stability is discussed, for a class of high_order cascade nonlinear systems having zero dynamics. Using adding power integrator techniques, the ADD problems via a smooth static state feedback is solved.

Review of a New IR Nonlinear Optical BaGa_4Se_7 Crystal

A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger technique.This new crystal has advantages of high nonlinear optics（NLO） coefficients,high laser damage thresholds,and wide transparent regions.The Ba Ga4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz regions.In this paper,the crystalline structure and synthetic method of the Ba Ga4Se7 crystal are introduced.The refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also obtained.The terahertz difference frequency generation（THz-DFG） characteristics based on the BaG a4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are calculated.The application of Ba Ga4Se7 crystals in terahertz wave generation is also discussed.

Adaptive adjustment of iterative learning control gain matrix in harsh noise environment

For the robustness problem of open-loop P-type iterative learning control under the influence of measurement noise which is inevitable in actual systems, an adaptive adjustment algorithm of iterative learning nonlinear gain matrix based on error amplitude is proposed and two nonlinear gain functions are given. Then with the help of Bellman-Gronwall lemma, the robustness proof is derived. At last, an example is simulated and analyzed. The results show that when there exists measurement noise, the proposed learning law adjusts the learning gain matrix on line based on error amplitude, thus can make a compromise between learning convergence rate and convergence accuracy to some extent： the fast convergence rate is achieved with high gain in initial learning stage, the strong robustness and high convergence accuracy are achieved at the same time with small gain in the end learning stage, thus better learning results are obtained.

Soliton evolution and control in a two-mode fiber with two-photon absorption

Soliton dynamics are numerically investigated in a two-mode fiber with the two-photon absorption,and the effects of the two-photon absorption on the soliton propagation and interaction are demonstrated in different dispersion regimes.Soliton dynamics depend strictly on the sign and magnitude of the group velocity dispersion(GVD)coefficient of each mode and the strength(coefficient)of the two-photon absorption.The two-photon absorption leads to the soliton collapse,enhances the neighboring soliton interaction in both modes,and increases the energy exchange between the two modes.Finally,an available control is proposed to suppress the effects by the use of the nonlinear gain with filter.

Effects of gain nonlinearities in an optically injected gain lever semiconductor laser

The effects of gain compression on the modulation dynamics of an optically injected gain lever semiconductor laser are studied. Calculations reveal that the gain compression is not necessarily a drawback affecting the laser dynamics. With a practical injection strength, a high gain lever effect and a moderate compression value allow us to theoretically predict a modulation bandwidth four times higher than the free-running one without a gain lever,which is of paramount importance for the development of directly modulated broadband optical sources compatible with short-reach communication links.

Wavelength-Dependent Transient Characteristics Caused by Gain Saturation in Highly Nonlinear Fiber-Based Raman Amplifiers

We have investigated the transient characteristics of discrete Raman Amplifiers and found that the response time caused by gain saturation is dependent upon the wavelength, which corresponds to the effective length of the pump light.