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Planar laser-induced fluorescence (PLIF) is a crucial spectroscopic technique for measuring minor species [e.g., hydroxyl (OH), methylene (CH), and nitric oxide (NO) radicals] in combustion research, owing to its non-intrusive nature and high sensitivity. However, laser energy attenuation due to absorption poses significant challenges to its application under high-pressure conditions, which may cause asymmetric image intensity distribution along the light propagation direction. An absorption correction method for OH PLIF based on the concept of maximum number density is proposed in the present study. This method offers several key advantages, including simplicity, high accuracy, and versatility, allowing for correcting both time-averaged and instantaneous OH PLIF images. OH PLIF data obtained from a centrally staged combustor at elevated pressures (i.e., 0.3, 0.6, and 1.0 MPa) are utilized to validate the method. Correction for the time-averaged PLIF images achieves a much more symmetric distribution of OH, revealing the overall flame structures that would not have been completely visualized from the original images. The fronts of the pilot and main stage flames have also been recovered from the corrected instantaneous images. This correction algorithm provides an effective way of enhancing data quality for high-cost OH PLIF measurements at pressurized conditions. [ABSTRACT FROM AUTHOR]

Modulation of the refractive index in a medium by external stimuli enables fast and reversible control of light propagation. This technology for controlling light has led to new discoveries in a wide range of research fields from physics to life sciences and has played a major role in the development of photonics devices. In this article, we focus on ultrasound as an external stimulus and have devised a method to control the refractive index of a medium using ultrasound. Our research group has previously discovered that a giant refractive-index gradient (Δn on the order of 10−2) was induced when water was irradiated with high-frequency (100 MHz range), high-intensity (on the order of MPa) ultrasound. Here, we report ray-tracing simulations in a medium with a refractive-index gradient induced by ultrasonic radiation. A numerical model of the refractive-index gradient was developed based on the experimental data, and ray-tracing simulations were performed using the Euler–Lagrange equation. The ray-tracing simulation results were close numerically to the profiles of the laser beam observed in the experiment when the laser beam was incident on the refractive-index-gradient medium. [ABSTRACT FROM AUTHOR]

We report a two-layer Mueller matrix model of polarized light propagation through layered human skin. Our model is based on single scattering approximation and the fact that the main scatterers in the top layer are various types of cells and the scatterers beneath it consist of fibers. By modeling the first layer mainly with spherical particles inducing the characteristics represented by Mueller matrices of depolarization and diattenuation, the second layer mainly with cylindrical scatterers inducing the retardance caused by scattering and birefringence, and considering the effects of the first layer to the second one, and the equal weight of contributions from both layers to a scatterer, it is possible to separate polarization properties of the medium induced by light propagation and scattering processes. One advantage of our model is that its extension to multi-layer tissues is straightforward. Polarization effects of human nail fold are identified. [ABSTRACT FROM AUTHOR]

Photoelectron angular distributions (PADs) produced from the photoionization of chiral molecules using elliptically polarized light exhibit a forward/backward asymmetry with respect to the optical propagation direction. By recording these distributions using the velocity-map imaging (VMI) technique, the resulting photoelectron elliptical dichroism (PEELD) has previously been demonstrated as a promising spectroscopic tool for studying chiral molecules in the gas phase. The use of elliptically polarized laser pulses, however, produces PADs (and consequently, PEELD distributions) that do not exhibit cylindrical symmetry about the propagation axis. This leads to significant limitations and challenges when employing conventional VMI acquisition and data processing strategies. Using novel photoelectron image analysis methods based around Hankel transform reconstruction tomography and machine learning, however, we have quantified—for the first time—significant symmetry-breaking contributions to PEELD signals that are of a comparable magnitude to the symmetric terms in the multiphoton ionization of (1R,4R)-(+)- and (1S,4S)-(−)-camphor. This contradicts any assumptions that symmetry-breaking can be ignored when reconstructing VMI data. Furthermore, these same symmetry-breaking terms are expected to appear in any experiment where circular and linear laser fields are used together. This ionization scheme is particularly relevant for investigating dynamics in chiral molecules, but it is not limited to them. Developing a full understanding of these terms and the role they play in the photoionization of chiral molecules is of clear importance if the potential of PEELD and related effects for future practical applications is to be fully realized. [ABSTRACT FROM AUTHOR]

In this paper, we study the Radhakrishnan–Kundu–Lakshmanan equation (RKLE) that plays a key role in modeling the nonlinear propagation of the light pulses. Two novel methods namely Wang's Bäcklund transformation-based method and Wang's direct mapping method are employed to construct the diverse exact optical soliton solutions. Abundant exact solutions like the bright soliton solution, dark soliton solutions, singular soliton solutions, algebraic solitary wave solutions and the singular periodic wave solutions expressed in the form of the rational function type, double-exp function type, Sin-Cos function type, Tan function type, Cot function type, Sinh-Cosh function type, Tanh function type, Coth function type, Sech function type, Csch function type, Sec function type and Csc function type are obtained. The dynamics of the different exact solutions are presented through the 3D plot, contour and 2D curve, and the corresponding physical interpretations are elaborated in detail. It is confirmed that the proposed methods are effective and powerful, and can be adopted to construct the optical solitons of the other PDEs arising in the optical physics. [ABSTRACT FROM AUTHOR]

In this study, we investigate the (3+1) q-deformed tanh-Gordon equation due to its importance in the context of mathematical physics. It describes solitonic solutions in quantum field theory; it can sometimes be used in condensed matter physics to describe interactions between particles in magnetic materials or superconductors; it can model light propagation in nonlinear optical fibers or photonic crystals where the refractive index has a q-deformed structure; and it also can be applied in studying shock waves, turbulence and rogue waves where the deformation introduces corrections to classical wave phenomena. Utilizing the ( G ′ ω G ′ + G + r) -expansion technique, we derive novel analytical solutions that enhance our understanding of the underlying dynamics. Additionally, we employ a finite element method (extended cubic B-spline method) to validate our analytical findings and explore the behavior of the q-deformed equation under different parameter regimes. Our results demonstrate the versatility of the q-deformed framework in generating rich optical phenomena, paving the way for future research in both theoretical and applied physics. [ABSTRACT FROM AUTHOR]

Light transmission through a multimode fiber (MMF) has gained major importance for imaging and manipulation. The majority of phase retrieval algorithms used for a MMF implicitly assume light propagation to be described by a unitary operation, yet the transmission matrix of a multimode fiber is inherently non‐unitary. It is demonstrated that this erroneous assumption can impede the performance of many commonly used MMF phase retrieval algorithms and demonstrate that the weighted Yang–Gu algorithm outperforms other phase retrieval algorithms in this scenario. Once accounted for, the non‐unitary property of the transmission matrix can be leveraged to generate intricate intensity and phase patterns at the output of the fiber, and shape specific output fields. This is experimentally demonstrated by generating Laguerre–Gaussian beams that carry orbital angular momentum, and by forming images in planes offset from the distal end of the fiber facet. [ABSTRACT FROM AUTHOR]

This research focuses on the nonlinear coupled Davey–Stewartson Fokas system, which models pulse propagation in monomode optical fibers. In order to find the novel periodic and solitary wave solutions of the nonlinear coupled Davey–Stewartson Fokas system, we have employed two effective mathematical techniques named as the Sine‐Gordon expansion method and the simple equation method. We found after researching into previous literature that these novel solutions are unique and have never been reported. Some 3D and 2D graphs are also used to discuss the dynamical behavior of these new solutions. [ABSTRACT FROM AUTHOR]

Fiber optic research continues to develop due to the need for fast information technology. The input signal in an optical fiber is in the form of a soliton wave that propagates in the fiber with a balanced index of refraction, dispersion, and diffraction. Fiber optics may lose some of the signal over time if they solely use a nonlinear refractive index. This study aims to examine into the dynamics and decoherence of multi-peak solitons caused by electromagnetic signal attenuation and potential trap in the propagation via optical fibers. The methods used start with the stationary solution of the nonlinear Schrödinger Cubic Quintic equation, the Newton-Raphson method, and the fourth-order Runge-Kutta. In stationary solutions, the p (state energy) and ρ (Lèvy index) values affect the number, pulse width, and height of soliton peaks. Increased p and ρ values lead to increased instability, causing the data transmitted into the optical fiber to collapse and become unreadable by the receiver. In the excited state (p > 0), the decoherence phenomenon occurs and causes wave instability and destruction. In term of energy intensity, a stable form of transmission in the ground state has a pattern of continuously weakening, decreasing, and smoothing, while in the excited state there is a spike in the intensity of the electromagnetic wave. Based on this study, multi-peak solitons can only be applied for propagation distances, which tend to be short due to their dynamics and decoherence. [ABSTRACT FROM AUTHOR]

Controlling light at subwavelength scales is crucial in nanophotonics. Hyperbolic polaritons, supporting arbitrarily large wavevectors, enable extreme light confinement beyond the diffraction limit. Traditional hyperbolic metamaterials suffer from high losses due to metallic components, while natural low-loss hyperbolic phonon polaritons are limited to the mid-infrared range. Some hyperbolic materials at visible frequencies have been studied, but they are either very lossy or only feature out-of-plane hyperbolicity. Here, we demonstrate the presence of low-loss, in-plane hyperbolic plasmon polaritons in the visible and near-infrared in thin-films of MoOCl2, a natural van der Waals crystal. The polariton dispersion is predicted based on the framework of light propagation in biaxial media and experimentally confirmed by real space nano imaging on exfoliated flakes. MoOCl2 constitutes an ideal material platform for visible range applications leveraging the unboundedness of hyperbolic modes, such as hyperlensing, Purcell factor enhancement, and super-resolution imaging, without the drawbacks of metamaterials. Hyperbolic polaritons in van der Waals materials are light-matter excitations holding potential for nanophotonics applications, but they are mostly observed in the mid-infrared range. Here, the authors report the observation of low-loss in-plane hyperbolic plasmon polaritons in MoOCl2 thin-films at visible and near-infrared frequencies. [ABSTRACT FROM AUTHOR]

A novel design and approach for the realization of liquid crystal optical waveguides using photopatterning as a manufacturing method is presented. The developed method is used to demonstrate straight waveguides of different widths and curved waveguides with different radius of curvature. The waveguides are terminated with +1 or −1 surface defects through which the light incouples/outcouples. The effect of the straight waveguide thickness and the radius of curvature of the curved waveguides on the attenuation of the light in the waveguide is experimentally explored. The experiments are supported with numerical simulations of light propagation through both types of waveguides and outcoupling out of the straight waveguides. Furthermore, the effect of the size of the −1 defect terminations on the outcoupling efficiency is explored using simulations. Based on the presented design and manufacturing approach, liquid crystal optical waveguides of various shapes can be realized accurately with low‐cost. [ABSTRACT FROM AUTHOR]

1D models with topological non‐trivial band structures are a simple and effective way to study novel and exciting concepts in topological photonics. In this work, the propagation of light‐matter quasi‐particles, so‐called exciton‐polaritons, is studied in waveguide arrays. Specifically, topological states are being investigated at the interface between dimer chains, characterized by a non‐zero winding number. In order to exercise precise control over the polariton propagation, non‐resonant laser excitation, as well as resonant excitation, are studied in transmission geometry. The results highlight a new platform for the study of quantum fluids of light and non‐linear optical propagation effects in coupled semiconductor waveguides. [ABSTRACT FROM AUTHOR]

Fluorinated polyurethaneimide (PUI) electro-optic waveguide polymer with polyurethane and polyimide chain segment structures was synthesized by stepwise polymerization using the synthesized amino ester oligomer pu and imide oligomer pi as monomers. Since the main chain structure of the synthesized PUI had the functionality of both polyurethane and polyimide chain segment structures, it combines the excellent thermal and film-forming properties of polyurethanes and polyimides, as well as lower optical transmission loss in the near-infrared wavelength band. The glass transition temperature (Tg) of PUI was 182 °C, and the 5% heat loss decomposition temperature was 325 °C. The PUI had good optical properties with an optical propagation loss of 1.10 dB/cm and an electro-optic (EO) coefficient (γ33) of 86 pm/V at a wavelength of 1550 nm. A Mach-Zehnder interferometric polymer waveguide EO modulator had been designed and fabricated by using the PUI as a waveguide electro-optic core layer. The prepared polymer waveguide EO modulator showed a good electro-optic modulation response at a wavelength of 1550 nm under an applied 1 kHz sinusoidal modulation signal. The results showed that the synthesized PUI met the performance requirements for the preparation of polymer optical waveguide devices and was a polymer electro-optic waveguide material with good overall performance. [ABSTRACT FROM AUTHOR]

As an advanced signal source, laser is very suitable for various photonic devices but implementing tunability of wavelength is more challenging. Herein, the study designs and synthesizes boron difluoride derivative tBuBF2, systematically studying the impact of assembly behavior on laser performance. The laser test results indicate that the emission wavelength of tBuBF2 microcrystals can be controlled by varying the length of the microcrystals, with the shorter wavelength of 0–1 vibronic lasing emission at 444 nm and the longer wavelength of 0–2 lasing emission at 468 nm. Mechanistic studies reveal that laser color change comes from an increase in optical propagation losses due to self‐absorption at the 0–1 vibronic band. Furthermore, CBP@tBuBF2 microcrystals constructed by doping with 4,4′‐bis(9‐carbazolyl)‐1,10‐biphenyl (CBP) as the guest molecule, which primarily exhibits 580 nm exciplex yellow emission while retaining weak blue emission. Moreover, it is demonstrated that the laser emission only occurred within the 0–2 vibronic band in the blue region owing to the increased self‐absorption phenomenon with 0–1 band, thus achieving controllable dual‐wavelength and exciplex emission for laser concealment. This work expands novel regulation strategy available for laser behavior control by enhancing the self‐absorption process, describing structure‐property relationships that will guide the design of advanced laser materials. [ABSTRACT FROM AUTHOR]

Laser interferometry plays a crucial role in laser ranging for high-precision space missions such as GRACE (Gravity Recovery and Climate Experiment) Follow-On-like missions and gravitational wave detectors. For such accuracy of modern space missions, a precise relativistic model of light propagation is required. With the post-Newtonian approximation, we utilize the Synge world function method to study the light propagation in the Earth's gravitational field, deriving the gravitational delays up to order c −4. Then, we investigate the influences of gravitational delays in three inter-satellite laser ranging techniques, including one-way ranging, dual one-way ranging, and transponder-based ranging. By combining the parameters of Kepler orbit, the gravitational delays are expanded up to the order of e 2 (e is the orbital eccentricity). Finally, considering the GRACE Follow-On-like missions, we estimate the gravitational delays to the level of picometer. The results demonstrate some high-order gravitational and coupling effects, such as c −4-order gravitational delays and coupling of Shapiro and beat frequency, which may be non-negligible for higher precision laser ranging in the future. [ABSTRACT FROM AUTHOR]

Owing to its topological properties and band collapse, Floquet helical photonic lattices have gained increasing attention as a purely classical setting to realize the optical analogues of a wide variety of quantum phenomena. We demonstrate both theoretically and numerically that light propagation in an appropriately designed helical superlattice can exhibit spatial photonic Zitterbewegung effect, i.e., a quiver spatial oscillatory motion of the beam center of mass around its mean trajectory, in both one- and two-dimensional cases. The lattice spacing determines the effective coupling strength between adjacent helical waveguides, and further drastically not only affects the oscillation amplitude and frequency, but also invert their direction of drift when the effective coupling strength is tuned from positive to negative. Complete arrest and inversion of the drift direction of Zitterbewegung effect are reported. [ABSTRACT FROM AUTHOR]

Controlling the propagation of light in the form of surface modes on miniaturized platforms is crucial for multiple applications. For dielectric multilayers that sustain Bloch surface waves at their interface to an isotropic dielectric medium, a conventional approach to manipulate them exploits shallow surface topographies fabricated on top of the truncated stack. However, such structures typically exhibit low index contrasts, making it challenging to confine, steer, and guide the Bloch surface waves. Here, we theoretically and experimentally demonstrate a device for a Bloch surface wave platform that resonantly couples light from a cavity to a straight waveguide. The structure is designed using topology optimization in a 2D geometry under the effective index approximation. In particular, the cavity–waveguide coupling efficiency of the radiation emitted by an individual source in the cavity center is optimized. The cavity is experimentally found to exhibit a narrow resonant peak that can be tuned by scaling the structure. The waveguide is shown to guide only light that resonates in the cavity. Fully three-dimensional simulations of the entire device validate the experimental observations. [ABSTRACT FROM AUTHOR]

ABSTRACT This study focuses on the manipulation of soliton parameters within optical waveguides characterized by a dual‐power law refractive index, drawing similarities with published papers. The precise management of solitons holds significant importance in the field of fiber‐optical communication. While previous research has primarily concentrated on modifying soliton attributes such as amplitude and width, comparatively less attention has been dedicated to controlling the wave speed of solitons. In order to bridge this gap, the researchers adopted the employment of the nonlinear Schrödinger equation with time‐dependent dispersion and two power‐law nonlinearities, mirroring similar approaches found in published literature. By employing this methodology, the researchers successfully achieved active control over the wave speed of solitons in non‐uniform optical waveguides. To effectively handle the inherent complexities of the nonlinear system, two well‐established techniques, namely, the generalized Kudryashov method and the simple equation method, were utilized to derive solutions. These techniques have been previously employed and demonstrated in published papers, further enhancing the validity and reliability of the research findings. We discuss the traveling wave solutions by finding the fixed points of the dynamical planar system. [ABSTRACT FROM AUTHOR]

Light propagation in complex media results in strong scattering. While wavefront shaping (WFS) enables the focusing of light at depth, its speed is mainly limited by the frame rate of the area‐array detectors. The photodetector has been used to achieve fast focusing, but it cannot record sufficient speckle information, limiting its applications in multi‐point focusing and non‐invasive focusing. Here, a method for invasively or non‐invasively focusing through scattering media is proposed by using 1D speckle signals as feedback for wavefront shaping. Experimentally, not only invasive multi‐point focusing can be realized, but also by maximizing the contrast of linear fluorescent 1D speckle signals, non‐invasive focusing can be achieved, suggesting the effectiveness of the proposed method. This approach can be generalized to the utilization of linear array detectors in WFS and may hold interesting prospects for rapid focusing light within deep biological tissues. [ABSTRACT FROM AUTHOR]

Silicon‐based on‐chip broadband surface‐enhanced infrared absorption (SEIRA) is highly desired for integrated micromolecular detection systems, taking advantages of CMOS mass production, low cost, high sensitivity, etc. However, the silicon platform is difficult to operate in the mid‐infrared wavelength region above 4 µm where abundant fingerprint characteristics of biomolecules are located, because of the strong absorptions in silicon dioxide cladding above 4 µm. Here, a large‐core rib silicon waveguide‐integrated gradient nanoantenna array is proposed for broadband long‐wave infrared biomolecular detection. It is shown that Low loss propagation of light in the long‐wave infrared region up to 7 µm (1428 cm−1) in silicon photonics can be achieved while avoiding complex fabrication techniques. A gradient nanoantenna array is designed on the waveguide to achieve broadband enhancement from 5 to 7 µm (1428–2000 cm−1). Laser spectroscopy of bovine serum albumin on the chip is demonstrated, showing enhancement of absorbance by approximately ten times over laser transmission spectroscopy in the amide bands. Such a platform opens up a new horizon of silicon‐based on‐chip SEIRA biomolecular detection. [ABSTRACT FROM AUTHOR]

We investigated a diffraction optical waveguide structure with a double layer coupling configuration. This double layer-coupled diffraction optical waveguide structure modulates light information through wavefront modulation for propagation within the optical waveguide and then reproduces the light information through further wavefront modulation, thus achieving optical information transmission. Analysis indicates that the theoretical maximum field of view can reach 90° × 90°. With an actual field of view set to 53° × 53°, an entrance pupil size of 3.2 × 3.2 mm², an eye relief of 10 mm, and 50 pupil expansion, the system's total energy transmission efficiency is 37%, with field of view uniformity at 91% and uniformity within the eye movement range reaching 97%. [ABSTRACT FROM AUTHOR]

A numerical investigation of the impact of fourth-order dispersion in the dynamics of Gaussian pulse propagation in photonic crystal fiber is presented. Considering the importance of waveguide dispersion in photonic crystal fiber, higher-order dispersion, especially fourth-order dispersion, is found to be crucial and significantly affects the dynamics. To study the evolution of various pulse parameters during propagation, we adopt the generalized projection operator method to derive the pulse parameter equation. It is observed that the fourth-order dispersion is found to be critical and, hence, remarkably influences the dynamics. A detailed discussion is presented to give further insight into the impact of Fourth order dispersion. Different ansatz-like methods are also considered alongside the Gaussian ansatz. [ABSTRACT FROM AUTHOR]

In this article, we analyze the traveling wave solutions of the dimensionless time dependent Paraxial equation. In Paraxial approximation the partial differential approximation is responsible for optical wave propagation. The proposed equation is used when light or electric currents pass through optical systems such as lenses, mirrors, and optical fibers. An extended hyperbolic function method is used to construct traveling wave solutions. By using the proposed method in the Paraxial equation, different types of soliton solutions such as dark solitons, bright solitons, periodic solutions and singular soliton solutions are recovered. These solutions are obtained by carefully choosing the values of certain parameters involved in the method and model. Our findings are original and can greatly contribute to understanding the propagation of light waves. Some important requirements for the validity of solutions are also discussed. In addition, line plots and surface diagrams are presented to demonstrate the physical and behavioral significance of our findings for the proposed model. [ABSTRACT FROM AUTHOR]

The ability to transmit data at a high transmission rate is one of the main challenges that has limited the performance of visible light networking systems. In this paper, we present an eight-core photonic crystal fiber designed for multiplexing (MUX) operations at wavelengths of 1.32, 1.3, 1.54, 1.19, 1.4, 0.98, 1.35, and 1.1 µm to overcome this issue. Various MUX parameters, such as transmission rate and normalized power, are examined in this numerical study. A multiplexer is a device that enables multiple messages or signals to be conveyed simultaneously through a single communication channel. A specific type of optical fiber, called photonic crystal fiber (PCF), is used in this context, which has a cladding made of photonic crystals surrounding the fiber core. The fiber features a periodic arrangement of tiny air holes along its length, creating a low-loss periodic dielectric material known as a photonic crystal. In this new design, silica rods are employed instead of multiple air-hole zones along the fiber's length to adjust the coupling length between adjacent channels. The results indicate that after 5.5 mm of light propagation, the operating wavelengths can be effectively multiplexed. [ABSTRACT FROM AUTHOR]

Orientational ordered soft matter possessing diverse microstructures has become a focal point of scientific research and technological exploration, thanks to its advancements in serving as an indispensable optical platform enabling propagation of light with multidimensional and manipulatable states. Herein, a facile way is developed to manipulate the in‐plane light beam transition dynamics by harnessing a time‐variable nematic liquid crystal (NLC) film through the electrical‐field‐induced topological defects. The results show that the dynamic change of optical branched flow is associated with the growth in the correlation length of optical potential and the reduction in the density of topological defects. The optical branching can continuously transform to deterministic and tunable beam steering at the low‐defect‐density regime through annihilation kinetics of defects. The explored soft matter system provides an excellent planar platform for the fundamental physics of light interacting with topological defects and may offer new perspectives for novel optics elements toward the applications of soft matter photonics. [ABSTRACT FROM AUTHOR]

Perfect vector vortex beams play a very important role in understanding complex structured beams due to their vortex nature and nonuniform polarization profiles. However, the generation of these beams suffers from a limited number of topological charges, bulky optical setup, lack of color information, and limited control along the light propagation direction. To tackle these fundamental and technical challenges, a metasurface approach to generating multiple grafted perfect vector vortex beams (GPVVBs) along the light propagation direction. GPVVBs with different colors are observed by changing the observation plane is proposed. Their polarization profiles are indirectly confirmed through the unique features in the modulated intensity profiles with an analyzer. Furthermore, the dynamic control of these beams is realized by continuously changing the incident polarization. Simultaneous control of color and topological charges in GPVVBs along the longitudinal direction provides more degrees of freedom for carrying information and has the potential to impact quantum science, singular optics, and optical communications. [ABSTRACT FROM AUTHOR]

The different types of optical soliton solutions are investigated for the 2-dimensional nonlinear Schrödinger equation with an instantaneous Kerr nonlinearity. This equation contains the beam propagation in a multimode optical fiber with a parabolic index profile. Different soliton solutions are examined, such as Breather waves, Lump waves, Mixed types, Periodic cross kink, Multiwave, M-shape, M-shape rational one, two kinks, and rogue waves. To obtain these optical solitons, we apply the Hirota bilinear transformation approach. These results are spectral, temporal, and spatial features of ultrashort light pulses that can be controlled in novel ways by this kind of nonlinear multimode optical fiber, which is gaining popularity. Moreover, the 3-dimensional, 2-dimensional, and contour plots are drawn for some solutions that show their physical interactions by selecting different parameters. These results are very helpful for further study of dynamical systems. [ABSTRACT FROM AUTHOR]

This study investigates the dynamics of boomerang solitons and their interactions in three-mode fiber under the influence of inhomogeneous effects governed by three-coupled nonlinear Schrödinger (3-CNLS) equations in GVD and nonlinearity coefficients. Also, 3-CNLS equation can be used to investigate the optical soliton propagation in three-core fibers, which contain some potential applications in the optical fiber communication system. Using the Darboux transformation method with computer simulation, the two-bright boomerang soliton solutions are attained analytically for the dispersion and nonlinearity functions. The propagation and interaction properties of boomerang solitons are investigated, while the variable coefficients are adopted as linear functions. Various interaction scenarios are illustrated by plotted figures to reveal the importance of obtained soliton solutions. The physical significance of boomerang solitons can be understood from the displayed figures. The obtained results will be benefit soliton path control and soliton phase management in an inhomogeneous three-core optical fiber. [ABSTRACT FROM AUTHOR]

Non-Kerr media, twin-core nonlinear optical fibers and waveguides are widely applied in optical fiber communications. In order to model the effects of quintic nonlinearity for the ultrashort optical pulse propagation in a non-Kerr medium, twin-core nonlinear optical fiber or waveguide, a coupled variable-coefficient cubic-quintic nonlinear Schrödinger system is investigated in this paper. For the two components of the electromagnetic fields, on the basis of the existing Lax pair, we take a gauge transformation to convert a Lax pair into an Ablowitz-Kaup-Newell-Segur system. Then we acquire a system, which is equal to the original system. The N-fold Darboux transformation is derived based on our Lax pair, where N is a positive integer. Applying Taylor series, we derive the N-fold generalized Darboux transformation. The second- and third-order vector breather solutions are obtained via the generalized Darboux transformation method. All our results depend on the variable coefficients of the original system. Our results might be of some use in a non-Kerr medium, twin-core nonlinear optical fiber or waveguide system. [ABSTRACT FROM AUTHOR]

Lithium niobate on insulator (LNOI) is a promising material platform for applications in integrated quantum photonics. A low optical loss is crucial for preserving fragile quantum states. Therefore, in this study, we have fabricated LNOI rib waveguides with a low optical propagation loss of 0.16 dB/cm by optimizing the etching conditions for various parameters. The symmetry and smoothness of the waveguides on x‐cut LNOI are improved by employing a shallow etching process. The proposed method is expected to facilitate the development of on‐chip quantum photonic devices based on LNOI. [ABSTRACT FROM AUTHOR]

Strongly scattering media disrupt both the wavefront distribution and the polarization state of the incident light field. Controlling and effectively utilizing depolarization effects are crucial for optical applications in highly scattering environments, such as imaging through dense fog. However, current simulation models have difficulty simulating the evolution of vector light fields within scattering media, posing challenges for studying vector light fields in strongly scattering environments. Here, we propose the Vector Angular Spectrum (VAS) model for simulating the propagation of vector light fields within scattering media. By introducing the angular spectrum distribution of vector light scattering and polarization conversion mechanisms, this model can simulate the depolarization effects of vector light propagating through strongly scattering media. The VAS model has also been used to investigate the focusing of vector scattered light through scattering media. Furthermore, the simulation results of the model have been validated through experiments. The proposed VAS model is expected to play a role in the theoretical research of vector scattered light and optical applications in strongly scattering environments. [ABSTRACT FROM AUTHOR]

Spectral analysis of light is one of the oldest and most versatile scientific methods and the basis of countless techniques and instruments. Miniaturized spectrometers have recently seen great advances, but challenges remain before they are widely deployed. We report an integrated photonic spectrometer that achieves high performance with minimal component complexity by combining imaging of light propagation patterns in multi-mode interference waveguides with machine learning analysis. We demonstrate broadband operation in the visible and near-infrared, 0.05 nm spectral resolution, and an array of four spectrometers on a single chip. Two canonical applications are implemented: spectral analysis of the solar spectrum with neural network reconstruction and detection of Rayleigh scattering from microbeads on an optofluidic chip using principal component classification. These results illustrate the potential of this approach for high-performance spectroscopy across disciplines. [ABSTRACT FROM AUTHOR]

Free space optical (FSO) communication has shown promising advantages among other wireless schemes. It provides a very high data rate, freedom from licensing, low cost of deployment and requires low power. FSO is a technology that has undergone rapid development over the last several years. These communication systems are a line-of-sight technology in which information is transmitted through the atmosphere on modulated laser beams or light-emitting diode (LED) beams. When FSO technology was first introduced, it was seen as an attractive option to bridge the "last mile bottleneck" that is present in many of today's optical fiber-based networks. As compared to existing radio frequency (RF) based wireless systems, this technology possesses multiple advantages, such as high bandwidth, license-free band use, long operational range, spatial reusability, security and immunity to electromagnetic interference. The narrow and directional characteristics of a laser beam employed in FSO enable spatial reuse and make it hard to eavesdrop, thus raising the level of security. The use of light as carrier in this technology provides immunity to electromagnetic interference. Despite its many advantages, this technology is susceptible to some weather conditions, such as fog, rain, sleet and snow, and to misalignment of transmitter–receiver terminals. Atmospheric conditions will impair the propagation of an optical signal because the propagation of light may undergo absorption and scattering. Pointing error caused by misalignment of the transceivers is another major challenge in FSO communication system. The pointing error may result in degradation or even total loss of the received signal. This error may arise because of transceiver sway, platform vibration, the motion of mobile stations, errors or uncertainties in the tracking system. Another type of pointing error is beam wandering caused by the in-homogeneity of large-scale eddies in the atmosphere (i.e., atmospheric turbulence), where the transmitted beam may deviate from its intended path. This survey paper focuses on the systems involved in the alignment of the transmitter and the receiver so that the maximum amount of power is collected by the receiver and the analysis of beam profile in various atmospheric conditions and their mitigation methods. [ABSTRACT FROM AUTHOR]

This paper explores the propagation loss in waveguides on directly bonded InP/Si substrates, using numerical simulations to understand the effect of voids within the waveguide structure. Using COMSOL Multiphysics, we developed a model to simulate light propagation, focusing on how void characteristics such as diameter and angle influence the propagation loss. Our findings reveal a correlation between void dimensions and the increased threshold current density in separate confinement heterostructure multiple quantum well laser diodes, thereby providing insights into optimizing waveguide design for enhanced laser performance on InP/Si substrates. This research underscores the critical role of substrate bonding quality in minimizing internal losses and improving device efficiency. [ABSTRACT FROM AUTHOR]

The paper contains a detailed analysis of the formation of an auroral spiral based on hitherto not published observations by the all‐sky camera in Kilpisjärvi, Northern Finland. We conclude that spirals appearing during a substorm form by a modification of the interface between tail and magnetosphere, the location of the generator current of the westward electrojet. Driven by the arriving flow bursts, this current is subject to ruptures by the appearance of a sequence of hook‐like structures. These structures can move eastward with speeds up to 3 km/s. The propagation is attributed to a constructive magnetic fracture process driven from behind by the power of the arriving flow bursts. Poleward bending and extension of a hook‐like structure, followed by a turning to the west and then equatorward, is the first step in spiral formation. It becomes the primary spiral arm, if a poleward arm grows out of weaker auroral structures, poleward and eastward of it. We suggest that the upward field‐aligned currents related to the bright spiral arms are largely balanced by adjacent downward currents. The electric fields associated with the connecting Pedersen currents are consistent with the counter‐clockwise motion. An important additional ingredient in the observed configuration is an eastward directed flow field, which is the generator of an additional upward current and possibly crucial for the spiral formation. Electric field data from literature throw confusing light on the propagation of a spiral, whether like a vessel in the ocean or by incorporating the magnetic flux ahead of it. Plain Language Summary: Auroral spirals are a fascinating phenomenon in the night sector during substorms. An event, observed by the all sky camera in Kilipisjärvi, is interpreted in the light of the physical processes at substorm onset. The forces exerted by an arriving flow burst on the magnetic field of the near‐dipolar magnetosphere generate an eastward directed current, which is the generator of the auroral electrojet (AEJ). This current can be broken into sections by an instability suggested to occur at strong flow gradients. Out of such sections, a spiral may form in two steps. First, a hook‐like structure, arising from the eastern end of the section, will extend poleward, then westward and finally equatorward thus forming the primary spiral arm. The poleward arm grows out of residues of the rupture process by draping themselves around the upper end of the primary arm. The luminous spiral arms, generated by upward currents, must be closely accompanied by downward currents located in the dark regions of the spiral. The electric fields, connected with the current closure in the ionosphere, are consistent with the counter‐clockwise sense of spiral formation. The creation of convolved auroral forms such as spirals serves an enhanced dumping of the entering energy. Key Points: Ruptures of the generator current lead to the formation of hook‐like structures out of which a spiral can evolveA primary spiral arm extending poleward in a counter‐clockwise sense is completed into a spiral by reformation of residues from the ruptureThe upward field‐aligned currents, which are associated with the luminous structures, are largely balanced by adjacent downward currents [ABSTRACT FROM AUTHOR]

The well-known formalism for Sum-Frequency Generation (SFG) reflected or transmitted by a three-layer system involves three equations defining the emitted SFG intensity, the effective nonlinear susceptibility, and a set of Fresnel factors specific to the three-layer system. We generalize the equations to an N-layer system, where all media have non-vanishing thicknesses, by leaving the first two equations unchanged and modifying only the Fresnel factors. These universal Fresnel factors bear all the complexity of light propagation and interference in the system, in amplitude and phase. They are analytically known anywhere in the N-layer system, either at any interface or in any of the bulks, and share common expressions for the three beams, incoming or emitted, of the SFG process in reflection. Enclosing an ultrathin layer (e.g., a molecular monolayer) in the system does not modify the Fresnel factors except for boundary conditions at this layer, as in the three-layer case. Specific rules are elaborated to simplify systems containing macroscopic layers. Equations for the four- and five-layer systems are explicitly provided. Simulations in the four-layer system allow for the recovery of the results of the transfer matrix formalism at a lower complexity cost for SFG users. Finally, when several interfaces in the system produce SFG signals, we show that it is possible to probe only the most buried one by canceling all the SFG responses except at this last interface, generalizing the results of the three-layer system. [ABSTRACT FROM AUTHOR]

Abstract We explore the dynamics of nonlinear parametric generation and light beam propagation in a Landau-quantized graphene structure with three energy levels interacting with two laser pulses, utilizing the Maxwell-Bloch equations. By applying a laser field to one transition of the graphene sample while keeping the second beam initially absent, the distinctive preparation of the graphene sample, coupled with its weak interaction with laser radiation, results in the parametric generation of a new laser beam in a different transition. We investigate the influence of diverse system parameters on both the efficiency of the generated beam and the propagation dynamics of both beams. Our findings reveal that manipulating these parameters can induce oscillations in the intensity of propagated beams, mitigate absorption losses during propagation allowing for earlier relaxation, and enhance the efficiency of energy transfer from the initial to the generated beam. Additionally, we demonstrate the transfer of optical vortices within the graphene ensemble by introducing an optical vortex to the initial beam. This scheme holds promise for applications in high-dimensional quantum information processing.

Abstract We explore the propagation of structured vortex laser beams-shaped light carrying orbital angular momentum (OAM)-through complex multiple scattering medium. These structured vortex beams consist of a spin component, determined by the polarization of electromagnetic fields, and an orbital component, arising from their spatial structure. Although both spin and orbital angular momenta are conserved when shaped light propagates through a homogeneous, low-scattering medium, we investigate the conservation of these angular momenta during the propagation of Laguerre–Gaussian (LG) beams with varying topological charges through a turbid multiple scattering environment. Our findings demonstrate that the OAM of the LG beam is preserved, exhibiting a distinct phase shift indicative of the ‘twist of light’ through the turbid medium. This preservation of OAM within such environments is confirmed by in-house developed Monte Carlo simulations, showing strong agreement with experimental studies. Our results suggest exciting prospects for leveraging OAM in sensing applications, opening avenues for groundbreaking fundamental research and practical applications in optical communications and remote sensing.

Photonic Crystal Fiber (PCF) constructions, controlled light propagation for measuring amplitude, phase, polarization and wavelength of the spectrum, and PCF-incorporated interferometry techniques are the foundations upon which sensors operate. But the existing PCF techniques have very large stretching that tends to be difficult to align due to the cross-polarization mode of the optical fiber structure. Hence, the novel Polymer graphene-based Hexagonal cladding is designed by using a hexagonal hollowed core and a cladding material of Polymethyl methacrylate reinforced with gyroidal graphene which increases confinement strength. Once the crystal structure is designed, normally the presence of substrate the Q-factors is degraded. On substrates, Q-factors are enhanced by fine-tuning the position of the neighboring holes. Hence, the novel Bilayer Grating Stratum solves the degrading issues in Q-factors, which utilizes a Silicon polyamide-coated FBG in the crystal that is incorporated using the Femto-laser technique thereby increasing the wavelength tenability. To identify the electric field pattern, the designed structure is simulated in COMSOL software. Thus, the proposed system has a high sensitivity of 22 with a low material loss of 0.1% and a low response time of 0.2 s. [ABSTRACT FROM AUTHOR]

We demonstrate chip-scale sub-Doppler spectroscopy in an integrated and fiber-coupled photonic-metasurface device. The device is a stack of three planar components: a photonic mode expanding grating emitter circuit with a monolithically integrated tilt-compensating dielectric metasurface, a microfabricated atomic vapor cell, and a mirror. The metasurface photonic circuit efficiently emits a 130 μm wide (1 / e 2 diameter) collimated surface-normal beam with only −6.3 dB loss and couples the reflected beam back into the waveguide and connecting fiber, requiring no alignment between the stacked components. We develop a simple model based on light propagation through the photonic device to interpret the atomic spectroscopy signals and explain spectral features covering the full Rb hyperfine state manifold. The demonstration of waveguide-to-waveguide coupling through the vapor cell paves the way for atomic ensembles to be used as components in complex photonic integrated circuits, allowing the unique properties of atomic systems to be available for future highly miniaturized optical devices and systems. [ABSTRACT FROM AUTHOR]

We explore the dynamics of nonlinear parametric generation and light beam propagation in a Landau-quantized graphene structure with three energy levels interacting with two laser pulses, utilizing the Maxwell-Bloch equations. By applying a laser field to one transition of the graphene sample while keeping the second beam initially absent, the distinctive preparation of the graphene sample, coupled with its weak interaction with laser radiation, results in the parametric generation of a new laser beam in a different transition. We investigate the influence of diverse system parameters on both the efficiency of the generated beam and the propagation dynamics of both beams. Our findings reveal that manipulating these parameters can induce oscillations in the intensity of propagated beams, mitigate absorption losses during propagation allowing for earlier relaxation, and enhance the efficiency of energy transfer from the initial to the generated beam. Additionally, we demonstrate the transfer of optical vortices within the graphene ensemble by introducing an optical vortex to the initial beam. This scheme holds promise for applications in high-dimensional quantum information processing. [ABSTRACT FROM AUTHOR]

Photons with zero rest mass are impossible to be stopped. However, a pulse of light can be slowed down and even halted through strong light-matter interaction in a dispersive medium in atomic systems. Exceptional point (EP), a non-Hermitian singularity point, can introduce an abrupt transition in dispersion. Here we experimentally observe room-temperature storing light near an exceptional point induced by nonlinear Brillouin scattering in a chip-scale 90-μm-radius optical microcavity, the smallest platform up to date to store light. Through nonlinear coupling, a Parity-Time (PT) symmetry can be constructed in optical-acoustical hybrid modes, where Brillouin scattering-induced absorption (BSIA) can lead to both slow light and fast light of incoming pulses. A subtle transition of slow-to-fast light reveals a critical point for storing a light pulse up to half a millisecond. This compact and room-temperature scheme of storing light paves the way for practical applications in all-optical communications and quantum information processing. Exceptional point introduces the ability to control and tune light propagation. Here the authors demonstrate a 90-μm-radius optical microcavity to store light, induced by nonlinear Brillouin scattering at room temperature. [ABSTRACT FROM AUTHOR]

We manipulated and adjusted the absorption, dispersion, group index, and group velocity in a sodium atomic medium by controlling the strength and collective phase of the driving fields. The group index in these regions is calculated to be − 250,000. The group velocity v g in these locations is measured to be − 0. 1 2 × 1 0 − 4 m/s. An investigation is conducted on a negative delay of − 5 0 μ s in the sodium medium. The presence of negative delay and negative group velocity indicates the occurrence of superluminal propagation of light pulses within the medium. The negative group index is increased from − 1 × 1 0 5 to − 4 × 1 0 5 , and the negative delay time is increased from − 2 0 μ s to − 7 0 μ s, with the driving field E 2 having a Rabi frequency. The work presented in this paper has substantial implications for the fields of gravitational wave detection, radar technology, and temporal cloaks. [ABSTRACT FROM AUTHOR]

The Schrödinger equation depends on the physical circumstance, which describes the state function of a quantum‐mechanical system and gives a characterization of a system evolving with time. The essential focus of proposed research is to observe the solution for fractional generalized nonlinear Schrödinger (FGNS) equation using q‐homotopy analysis transform method (q‐HATM). The fractional order derivative is taken in the Atangana‐Baleanu (AB) sense. The physical behaviours of achieved solution for FGNS equation are discussed and sketch out graphically. The existence of the solution for the FGNS equation is presented through theorems 4.1 to 4.3. The proposed numerical simulations confirm the advantages of the AB derivative through q‐HATM. Few numerical experiments were carried out to validate the proposed method. Moreover, numerical simulations are carried out to verify efficiency and robustness of the derived results by considering two cases. [ABSTRACT FROM AUTHOR]

A high efficiency simulation method for propagation-based phase-contrast imaging, called directional macro-wavefront (DMWF), is developed with the aim of simulating high-energy phase-contrast imaging. This method takes both Monte Carlo and wave optical propagation into consideration. Traditional wave-optics-based simulation methods for phase-contrast imaging encounter unacceptable computational complexity when high-energy radiation is used. In contrast, this method effectively addresses this issue by using macro-wavefront integration. Several simulation examples using typical parameters of inverse Compton scattering sources are presented to illustrate the excellent energy adaptability and efficiency of the DMWF method. This method provides a more efficient approach for phase-contrast imaging simulations, which will drive the advancement of high-energy phase-contrast imaging. [ABSTRACT FROM AUTHOR]

In physical domains, Beta derivatives are necessary to comprehend wave propagation across various nonlinear models. In this research work, the modified Sardar sub-equation approach is employed to find the soliton solutions of (1+1)-dimensional time-fractional coupled nonlinear Schrödinger model with Beta fractional derivative. These models are fundamental in real-world applications such as control systems, processing of signals, and fiber optic networks. By using this strategy, we are able to obtain various unique optical solutions, including combo, dark, bright, periodic, singular, and rational wave solutions. In addition, We address the sensitivity analysis of the proposed model to investigate the truth that it is extremely sensitive. These studies are novel and have not been performed before in relation to the nonlinear dynamic features of these solutions. We show these behaviors in 2-D, contour 3-D structures across the associated physical characteristics. Our results demonstrate that the proposed approach offers useful results for producing solutions of nonlinear fractional models in application of mathematics and wave propagation in fiber optics. [ABSTRACT FROM AUTHOR]

Light propagation in a rotating medium undergoes drag in sync with the medium's rotational velocity at reduced group velocity of light. Conversely, at the greater group velocity, the drag manifests in the opposite direction. This phenomenon is recognized as rotary photon drag. In mediums with high dispersion, such as atomic mediums, light pulses undergo dragging effects leading to both linear and angular displacements in imaging. The manipulation and control of rotary photon drag involve employing beams of the Laguerre-Gaussian (LG) type. The careful examination of the ultranarrow absorption linewidth reveals significant anomalous dispersion due to detuning from resonance. Positive and negative group indices, along with delay times, are evident within the range of the absorption spectral Dirac Delta function. Through adjustments in the phase, relative detuning, and strength of the LG control fields, manipulation of maximum and minimum negative and positive group velocities occurs. Similarly, the control and modification of maximum and minimum photon drag are achieved using the phase, relative detuning, and strength of LG control fields. These tailored outcomes find practical applications in advanced technologies, encompassing molecular structure determination, specific modes of image coding, and design. [ABSTRACT FROM AUTHOR]

The human brain is a complex organ controlling daily activity. Present technique models have mostly focused on multi-layer brain tissues, which lack understanding of the propagation characteristics of various single brain tissues. To better understand the influence of different optical source types on individual brain tissues, we constructed single-layer brain models and simulated optical propagation using the Monte Carlo method. Based on the optical simulation results, sixteen optical source types had different optical energy distributions, and the distribution in cerebrospinal fluid had obvious characteristics. Five brain tissues (scalp, skull, cerebrospinal fluid, gray matter, and blood vessel) had the same set of the first three optical source types with maximum depth, while white matter had a different set of the first three optical source types with maximum depth. Each brain tissue had different optical source types with the maximum and minimum full width at half maximum. The study on single-layer brain tissues under different optical source types lays the foundation for constructing complex brain models with multiple tissue layers. It provides a theoretical reference for optimizing the selection of optical source devices for brain imaging. [ABSTRACT FROM AUTHOR]