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In this paper, we present a new design of solid-core photonic crystal fiber (PCF), a Ge20Sb5Se75 substrate with a hexagonal lattice structure. The fiber characteristics are studied in the long-wavelength range (from 1.5 µm to 7.0 µm). A full modal analysis and optical properties of designed photonic crystal fibers with lattice constant Λ and filling factor d/Λ are presented in terms of chromatic dispersion, effective refractive index, nonlinear coefficients, and confinement loss. All-normal and anomalous flat dispersion with high nonlinearity and low confinement loss are the outstanding advantages of these photonic crystalline fibers. From there, three optimal structures with Ʌ = 2.0 µm, d/Ʌ = 0.35; Ʌ = 2.5 µm, d/Ʌ = 0.3 and Ʌ = 3.0 µm, d/Ʌ = 0.3 are selected and analyzed in detail for application in supercontinuum (SC) generation.

In this research, new circular and hexagonal photonic crystal fibers (PCFs) filled with chloroform have been designed considering the difference in air hole diameters to optimize the characteristics of the fiber simultaneously. Effective mode area and confinement loss of five PCFs with optimal dispersion have been further studied to find the fiber with a great application value for supercontinuum generation (SCG). Generally, circular PCFs are dominant over hexagonal lattices because of their small effective mode area, low loss, and small dispersion. #CF1 fiber with a lattice constant (Ʌ) of 1.0 μm and filling factor (d1/Ʌ) of 0.65 has an all-normal dispersion with a low value of -1.623 ps/nm/km, a small effective mode area of 1.43 µm2, and a low loss of 2.472 dB/m at 0.945 µm. The effective mode area and confinement loss of #CF2 (Ʌ = 1.0 µm, d1/Ʌ = 0.7) are the smallest of proposed PCFs. #HF1 fiber (Ʌ = 1.0 µm, d1/Ʌ = 0.5) has a very flat dispersion curve in the 1-2 µm wavelength range and a rather small effective mode area. These are the most optimal fibers for two types of lattices, which are very suitable for near-infrared SCG.

The dispersion characteristics of As2S3 solid-core photonic crystal fibers were investigated with the change of structural parameters including filling factor (d/Λ) and lattice constant (Λ). Photonic crystal fiber obtained diverse dispersion including all-normal and anomalous dispersion with two zero-wavelengths dispersion at all values of lattice constant investigated. The dispersion value increases when the lattice constant increases and the filling factor decreases. Photonic crystal fiber has a flat dispersion curve and closeness to the zero-dispersion curve in the longwavelength range are advantages of this design. Based on the analysis of numerical simulation results, we have proposed two structures with optimal dispersion for the application of supercontinuum generation.

This article presents a comprehensive approach to integrate formation tracking control and optimal control for a fleet of multiple surface vehicles (SVs), accounting for both kinematic and dynamic models of each SV agent. The proposed control framework comprises two core components: a high‐level displacement‐based formation controller and a low‐level reinforcement learning (RL)‐based optimal control strategy for individual SV agents. The high‐level formation control law, employing a modified gradient method, is introduced to guide the SVs in achieving desired formations. Meanwhile, the low‐level control structure, featuring time‐varying references, incorporates the RL algorithm by transforming the time‐varying closed agent system into an equivalent autonomous system. The application of Lyapunov's direct approach, along with the existence of the Bellman function, guarantees the stability and optimality of the proposed design. Through extensive numerical simulations, encompassing various comparisons and scenarios, this study demonstrates the efficacy of the novel formation control strategy for multiple SV agent systems, showcasing its potential for real‐world applications. [ABSTRACT FROM AUTHOR]

This study presents a new square‐lattice photonic crystal fiber (PCF) with a nitrobenzene core. Considering the non‐uniformity of the air hole diameter, this new design allows the characteristic quantities to be optimized simultaneously to ensure near‐zero dispersion, a small effective mode area, and low loss for efficient spectral broadening. The spectrum broadens significantly at peak powers many times lower than in previous studies. Based on the obtained results, two optimal PCFs are proposed and validated in detail for supercontinuum generation (SCG). The first fiber #F1 operates in an all‐normal dispersion regime with a pump wavelength of 1.3 µm.It produces a spectral supecontinuum (SC) from 0.726 to 1.649 µm with a pulse duration of 90 fs and a peak power of 133 W. Meanwhile, the second fiber #F2 operates in anomalous dispersion regime with a pump wavelength of 1.61 µm. With a low peak power of 300 W and a pulse duration of 150 fs, the fiber #F2 provides SC generation with bandwidth from 0.805 µm to 3.970 µm. The proposed fibers are suitable for all‐fiber SC light sources, respectively, and may lead to new low‐cost all‐fiber optical systems. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrated the ability of a hexagonal photonic crystal fiber (PCF) with a hollow core infiltrated with nitrobenzene (C6H5NO2) to generate a broad SC spectrum at low peak powers. Due to the non-uniformity of the air hole diameters, our new design allows for simultaneous optimization of features, resulting in near-flat, near-zero dispersion, a small effective mode area, and low attenuation for efficient spectral broadening. We selected two optimal structures from the simulation results to analyze the nonlinear properties and supercontinuum generation. The first fiber, #HF1, with a lattice constant of 1.0 μ m and a filling factor of 0.45, operates in all-normal dispersion and produces spectral SC ranging from 0.81 μ m to 1.919 μ m with a pump wavelength of 1.56 μ m, a pulse duration of 90 fs, and peak power of 0.133 kW propagated in a 1 cm fiber length. The #HF2 fiber (lattice constant of 2.0 μ m, filling factor of 0.3) has an extended SC spectrum from 0.792 μ m to 3.994 μ m, a pump wavelength of 1.55 μ m, a pulse width of 110 fs, a peak power of 0.273 kW propagated in a 15 cm fiber length. The proposed fiber may be a new-generation optical fiber suitable for low-peak power all-fiber optical systems to replace glass-core glass fiber. [ABSTRACT FROM AUTHOR]

Due to the nonlinearities and dynamical properties of multisection web machines, it is essential to accomplish an appropriate mathematical model as well as design a compatible control scheme. A generalized fully driven web winding model is constructed taking unpredictable changes of moment of inertia and radius of rolls into consideration. In this article, a fractional‐order sliding surface algorithm‐based hierarchical control frame is applied to multisection web machines to deal with matched and mismatched uncertainties and disturbances. In addition, the Radius Basis Function neural network is deployed to estimate necessary system dynamics and the proposed control scheme taking advantage of first‐order low‐pass filters to produce virtual control signals without complicated calculation and attenuate the explosion of terms phenomenon. Finally, the semi‐global stability of the entire system is determined using Lyapunov's stability theory. The simulation results are presented to clarify the superior performance of robust control algorithm and approximation law in the presence of nonideal elements. [ABSTRACT FROM AUTHOR]