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With the rapid development of X‐ray free‐electron lasers (XFELs) that can generate ultrashort X‐ray pulses with a duration range from attoseconds to femtoseconds, the study of ultrashort XFEL pulse propagation in beamline systems is increasingly important, especially in dispersive beamline systems. We developed a 6D phase space ray‐tracing method to simulate pulse propagation in dispersive soft X‐ray optical systems. We validated this method by simulating a typical dispersive optical system: a grating monochromator. The simulation indicated that the spatiotemporal properties such as pulse front tilt, pulse front rotation and angular dispersion can be described. Using this approach, we performed a start‐to‐end simulation of the Shenzhen Superconducting Soft X‐ray Free Electron Laser (S3FEL) FEL‐1 beamline. Compared with the 3D pulse propagation method based on Fourier optics, this significantly reduces the simulation time. Our work provides a useful tool for X‐ray beamline systems design. This work develops a 6D phase space tracing module in the FURION software. The 6D phase space tracing provides a solution for the rapid simulation of ultrashort pulse propagation in X‐ray beamlines, especially in dispersive beamline systems.

This study explores analytical soliton solutions for the cubic–quintic time-fractional nonlinear non-paraxial pulse transmission model. This versatile model finds numerous uses in fiber optic communication, nonlinear optics, and optical signal processing. The strength of the quintic and cubic nonlinear components plays a crucial role in nonlinear processes, such as self-phase modulation, self-focusing, and wave combining. The fractional nonlinear Schrödinger equation (FNLSE) facilitates precise control over the dynamic properties of optical solitons. Exact and methodical solutions include those involving trigonometric functions, Jacobian elliptical functions (JEFs), and the transformation of JEFs into solitary wave (SW) solutions. This study reveals that various soliton solutions, such as periodic, rational, kink, and SW solitons, are identified using the complete discrimination polynomial methods (CDSPM). The concepts of chaos and bifurcation serve as the framework for investigating the system qualitatively. We explore various techniques for detecting chaos, including three-dimensional and two-dimensional graphs, time-series analysis, and Poincarè maps. A sensitivity analysis is performed utilizing a variety of initial conditions.

This research endeavors to generate a coherent and flat supercontinuum by designing and optimizing silicon core rectangular buried waveguides, featuring various width and height configurations of the core operating at the wavelength of 1550 nm. By estimating the effective index of the system, we compute the group velocity dispersion (GVD) parameters and higher-order dispersive terms, while concurrently determining the nonlinear Kerr coefficient crucial for pulse propagation. The propagation of chirp-free high-power Gaussian pulse is investigated through the proposed waveguide by numerically solving the generalized nonlinear Schrödinger equation. Our investigation reveals the attainment of a sufficiently broadened and notably flat supercontinuum for waveguides exhibiting a slightly positive GVD parameter. Leveraging the high nonlinearity of silicon-based waveguides relative to non-semiconductor counterparts, we achieve broad spectral coverage (~ 600 nm) over significantly shorter propagation lengths (~ mm), maintaining the favorable flatness and coherence parameters which can be extended even for a few mm length. To the best of our knowledge, such a rectangular/square Si core buried SOI waveguide has yet to be reported for the coherent supercontinuum generation in the telecommunication band.

Transient pulses generated by high-energy particles can cause soft errors in circuits, resulting in spacecraft malfunctions and posing serious threats to the normal operation of spacecraft. For integrated circuits used in space applications, it is necessary to first evaluate soft errors caused by transient pulses. Conventional soft-error-rate evaluation tools are designed to simulate the generation of transient pulses using many accurate models, while the propagation of transient pulses is primarily simulated by circuit-level simulation tools. Due to the limitations of simulation tools, conventional evaluation approaches are limited to the circuit scale. The simulation runtime is unbearable for large-scale integrated circuits. This paper presents an approach for evaluating the soft error rate using machine learning. A back propagation neural network is implemented in the proposed approach. It helps to determine the probability of transient pulse propagation. Compared with the conventional soft-error-rate evaluation results, the proposed approach demonstrates a strong correlation in both trend and magnitude. The average difference between the results obtained using the proposed evaluation method and the experimental results is 23.5%, which is 7.5% higher than that between the results obtained using the conventional evaluation method and the experimental results. Compared to the conventional evaluation method, the proposed approach improves the runtime by an order of magnitude. The proposed approach also benefits the locating of highly sensitive circuit nodes in large-scale integrated circuits. Circuit design and radiation hardening are both useful applications.

A key factor governing the mechanical performance of the heart is the bidirectional coupling with the vascular system, where alterations in vascular properties modulate the pulsatile load imposed on the heart. Current models of cardiac electromechanics (EM) use simplified 0D representations of the vascular system when coupling to anatomically accurate 3D EM models is considered. However, these ignore important effects related to pulse wave transmission. Accounting for these effects requires 1D models, but a 3D-1D coupling remains challenging. In this work, we propose a novel, stable strategy to couple a 3D cardiac EM model to a 1D model of blood flow in the largest systemic arteries. For the first time, a personalised coupled 3D-1D model of left ventricle and arterial system is built and used in numerical benchmarks to demonstrate robustness and accuracy of our scheme over a range of time steps. Validation of the coupled model is performed by investigating the coupled system’s physiological response to variations in the arterial system affecting pulse wave propagation, comprising aortic stiffening, aortic stenosis or bifurcations causing wave reflections. Our first 3D-1D coupled model is shown to be efficient and robust, with negligible additional computational costs compared to 3D-0D models. We further demonstrate that the calibrated 3D-1D model produces simulated data that match with clinical data under baseline conditions, and that known physiological responses to alterations in vascular resistance and stiffness are correctly replicated. Thus, using our coupled 3D-1D model will be beneficial in modelling studies investigating wave propagation phenomena.

This research paper illustrates a novel structure of the optical soliton wave solutions of nonlinear Schrödinger (NLS) equation with the higher-order (a model for the sub-10-fs-pulse propagation) by using the modified Khater method. Moreover, this research is studying the stability properties of obtained solutions to show their ability to apply in the model’s applications. The NLS equation with the higher-order describes the quantum aspects of a quantum-mechanical system. Some sketches are plotted to show more physical properties of the real, imaginary, and absolute obtained solutions. All obtained solutions are verified of its accuracy by putting them back into the original equation.

Laser energy absorption to fast electrons during the interaction of an ultra-intense (1020 W cm−2), picosecond laser pulse with a solid is investigated, experimentally and numerically, as a function of the plasma density scale length at the irradiated surface. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient.

Pulmonary hypertension (PH) is a debilitating disease that alters the structure and function of both the proximal and distal pulmonary vasculature. This alters pressure-flow relationships in the pulmonary arterial and venous trees, though there is a critical knowledge gap in the relationships between proximal and distal hemodynamics in disease. Multiscale computational models enable simulations in both the proximal and distal vasculature. However, model inputs and measured data are inherently uncertain, requiring a full analysis of the sensitivity and uncertainty of the model. Thus, this study quantifies model sensitivity and output uncertainty in a spatially multiscale, pulse-wave propagation model of pulmonary hemodynamics. The model includes fifteen proximal arteries and twelve proximal veins, connected by a two-sided, structured tree model of the distal vasculature. We use polynomial chaos expansions to expedite sensitivity and uncertainty quantification analyses and provide results for both the proximal and distal vasculature. We quantify uncertainty in blood pressure, blood flow rate, wave intensity, wall shear stress, and cyclic stretch. The latter two are important stimuli for endothelial cell mechanotransduction. We conclude that, while nearly all the parameters in our system have some influence on model predictions, the parameters describing the density of the microvascular beds have the largest effects on all simulated quantities in both the proximal and distal arterial and venous circulations.

In this work, unidirectional pulse propagation equation (UPPE) modeling is performed to study the nonlinear laser-mater interaction in silicon and Nd:Y3Al5O12 (Nd:YAG) crystals. The simulation results are validated with reported experimental results for silicon and applied to Nd:YAG crystals with experimental validation. Stress-induced waveguides are written in Nd:YAG crystals using 515 nm, 300 fs pulses at a 1 kHz repetition rate. Waveguides having a mean propagation loss of 0.21 ± 0.06 dB/cm are obtained, which is lower than the previous reported values for Type-II waveguides written in Nd:YAG crystals. The modeling and experimental results consistently show that the modification (waveguide track) depth increases with input energy. A detailed analysis is presented to control the modal properties of the waveguide in the context of UPPE simulation.

We theoretically study the few- and many-body dynamics of photons in chiral waveguides. In particular, we examine pulse propagation through an ensemble ofNtwo-level systems chirally coupled to a waveguide. We show that the system supports correlated multiphoton bound states, which have a well-defined photon numbernand propagate through the system with a group delay scaling as1/n2. This has the interesting consequence that, during propagation, an incident coherent-state pulse breaks up into different bound-state components that can become spatially separated at the output in a sufficiently long system. For sufficiently many photons and sufficiently short systems, we show that linear combinations ofn-body bound states recover the well-known phenomenon of mean-field solitons in self-induced transparency. Our work thus covers the entire spectrum from few-photon quantum propagation, to genuine quantum many-body (atom and photon) phenomena, and ultimately the quantum-to-classical transition. Finally, we demonstrate that the bound states can undergo elastic scattering with additional photons. Together, our results demonstrate that photon bound states are truly distinct physical objects emerging from the most elementary light-matter interaction between photons and two-level emitters. Our work opens the door to studying quantum many-body physics and soliton physics with photons in chiral waveguide QED.