Transactions in Optics and Photonics

Vortex Structures in Optical Fibers Under the Influence of Third-Order Dispersion and Self-Steepening Effect

Aneliya Dakova-Mollova — 2025-01-24

In this paper, we investigate for the first time the generation and formation of amplitude-type vortices propagating in single-mode optical fibers with a step-index profile under the influence of third-order dispersion and the self-steepening effect, also known as the dispersion of nonlinearity in the medium. The main model is based on the vector nonlinear amplitude equation, from which a system of two scalar partial differential equations is derived. These equations describe the evolution of the x- and y-components of the vector amplitude function of an optical pulse under the influence of higher-order nonlinear and dispersive effects. Exact analytical solutions of the resulting system of equations are obtained in the form of optical vortices. They exhibit amplitude-type singularities and appear as ring-like structures in the components of the laser pulses. Numerical simulations of the obtained solutions are performed. It is shown that the vortex parameter m is related to the number of these ring structures. Significant depolarization of the electric field is observed in the focal region of the laser radiation.

Complexity in Nonlinear and Quantum Optics by Considering Kolmogorov Derivatives and Change Complexity Information Measures

Dragutin T. Mihailović — 2025-01-17

One of the most challenging tasks in studying phenomena in nonlinear and quantum optics is determining the contributions of the complexities of individual components to the complexity of the entire system (master complexity). To examine these contributions, we considered this issue using information measures: Kolmogorov derivatives based on Kolmogorov complexity (KC) [KC spectrum, KC plane], change complexity (CC), and Lyapunov exponent (λ). We applied these measures to daily time series measured from 2003 to 2005 in Novi Sad (Serbia) for ultraviolet (UV) radiation, which represents a physical complex system, and water vapor pressure as individual components of that system. Based on the measures applied to UV radiation, we determined: (i) the level of chaos and randomness of the measured time series; (ii) the coordinates of points in the KC plane where master and individual amplitudes interact; and (iii) the range of UV radiation amplitudes in which changes in the interaction between the master and individual amplitudes are most pronounced.

Multisoliton Bound States in the Fourth-Order Concatenation Model of the Nonlinear Schrödinger Equation Hierarchy

I. M. Mendez-Zuñiga — 2025-03-10

We present a comparative analysis of exact soliton solutions that form multisoliton bound states arising in the hierarchy of the even-order nonlinear Schrödinger equations. Specifically, we consider two-soliton bound states in three models: the nonlinear Schrödinger equation, the fourth-order nonlinear equation, and the Lakshmanan-Porsezian-Daniel equation (LPDE). The LPDE may be viewed as one example of aninfinite concatenation hierarchy. The exact integrability of these equations is ensured by the Lax pairs constructed using the Ablowitz, Kaup, Newell, and Segur formalism of the Inverse Scattering Transform method. We confirm that the main property of solitons-to interact elastically and attract or repel each other in the collision region depending on the difference of their initial phases-is also preserved for LPDE solitons, and this property should take place in the entire hierarchy of concatenation models. We present the detailed dynamics of two-soliton bound states periodically breathing in space and time, the conditions of their formation, and analytical formulas for their oscillation periods in all the considered models.

Pure-Cubic Optical Soliton Perturbation Having Cubic-Quintic Law of Self-Phase Modulation via the New Kudryashov Integration Scheme

Muslum Ozisik — 2025-04-25

This paper secures dark and bright pure-cubic optical soliton solution to the perturbed third-order nonlinear Schrödinger’s equation having the cubic-quintic law nonlinearity of self-phase modulation with a couple of self-frequency shift and nonlinear dispersion perturbation terms which related to the Hamiltonian. The recently introduced new Kudryashov integration scheme is used to retrieve these soliton solutions. The suitable parameter selections for the existence of such solitons are also presented. In the second stage, the effects of these terms on the soliton forms are investigated by the cubic-quintic form of the problem under study. The findings obtained are supported by 3D and 2D figures and necessary explanations are presented.

Determination of the Baseline in the IR Spectra of External Reflection of Polymers for 3D Objects

V. M. Zolotarev — 2025-04-25

A methodology for forming a baseline of infrared (IR) spectra of external reflection for objects with a smooth non-flat surface is proposed. The procedure for forming a baseline provides conditions for the correct application of the Kramers-Kronig method. The method is tested in determining the complex refractive index of 3D objects made of polymeric materials.

Energy Exchange Between the Polarization Components of an Optical Pulse Under the Influence of Degenerate Four-Photon Parametric Processes

Zara Kasapeteva — 2025-04-25

The present paper investigates the process of energy exchange between the components of an optical pulse that is propagating in a nonlinear dispersive medium under the influence of degenerate four-photon parametric processes. The effects of self-phase modulation (SPM) and cross-phase modulation (XPM) have been taken into account. The obtained results demonstrate that no energy exchange takes place between the optical components of the pulse when the initial polarization is linear or circular. In the presence of initial elliptical polarization, energy exchange can be observed. The intensity of the energy transmission and its period can be determined using the values of the initial energies and the initial phase difference between the optical components of the pulse.

Optical Properties of Nanometer Epitaxial Nickel Oxide Films on LiNbO₃ Substrates

S. V. Averin — 2025-05-21

Nanometer epitaxial nickel oxide films have been successfully fabricated on LiNbO₃ substrates by magnetron sputtering. Optical properties of NiO films were studied in the wavelength range of 250-800 nm, and transmission and reflection spectra of these structures were simulated. The dispersion of the complex refractive index of the grown films was obtained, which ensures good agreement between the calculated and experimental transmission and reflection spectra. The band gap energy of NiO films was evaluated using Ultraviolet (UV)-visible spectroscopy. It is in the range of 3.57-3.59 eV. These studies allowed us to determine the thicknesses of the grown epitaxial films using optical methods and compare them with the results obtained based on the film growth rate and atomic force microscopy data.

On the Theory of Digital Modulation of Light Transmitted Through a Step-Index Optical Fiber

Sujit K. Bose — 2025-05-12

Analog modulation of wireless microwave/radio waves as well as optical waves through multiplexing is well established in practice due to technological breakthroughs. Such modulation techniques are well established in practice due to technological breakthroughs. The basic methods of modulation of a carrier wave are amplitude modulation (Amplitude Shift Keying (ASK)), frequency modulation (Frequency Shift Keying (FSK)), and phase modulation (Phase Shift Keying (PSK)). Quadrature Amplitude Modulation (QAM) is a combination of amplitude and phase modulation. Among these methods, simple amplitude modulation is particularly suitable and practical in fiber-optic communication, as extraneous errors are prevented by the protective jacket of the fiber cable—a scenario that is not applicable in wireless communication. The waveguide action in a cylindrical optical fiber enables the development of a theoretical model of light propagation undergoing amplitude modulation. This theory is presented in this paper for a step-index fiber consisting of a homogeneous core with a cladding of slightly lower refractive index. The input signal is assumed to be a sequence of N bits, which is multiplexed onto the carrier light wave, and a general formula is developed for the field intensity determined from the axial component of the Hertz vector of the associated electromagnetic wave at a receiving point. The expression of that field is represented in the form of a Fourier integral, which is evaluated using the Fast Fourier Transform (FFT) for simple numerical cases. The theory covers both single-mode fibers, which support only the fundamental propagation mode, as well as multimode fibers of larger diameters. The theory provides the characteristics of the wave at a distant receiving station when the input is in bit form, for which demodulation techniques are available. In addition, the theory provides a method of serial transmission of multiple bits in a sequence, provided that suitable demodulation techniques are available at the receiver end. A simple measure based on maximum field strength is suggested in the paper.

Improving the Photon-Electron Coupling Efficiency in GaN-Based Square Microdisks

Jing Zhou — 2025-08-04

In this work, two types of GaN-based square microdisks, which are suspended microdisks and microdisks with a porous bottom layer based on standard blue/green Light-Emitting Diode (LED) structures grown on Si substrates, are studied. At room temperature, resonant emission was observed in the suspended square microdisk, and the porous microdisk achieved optically pumped lasing at a wavelength of 479 nm with a threshold of 4.37 mW. Optical field simulations reveal that the bridges of the suspended microdisk not only facilitate the transport of light from the microdisk into the bridges for directed propagation but also have no impact on the internal light field distribution. On the other hand, the lasing results of the microdisks with the porous bottom layer demonstrate that the presence of the porous layer enables a high degree of photon confinement within the active region. The results from both types of microdisks confirm that the electron-photon coupling efficiency can be significantly enhanced in the square microcavities, and furthermore that the optical signals can be effectively transmitted through the bridges of the suspended microdisks. This work presents a highly promising approach for Si-based optoelectronic integration.

Thermoluminescence Properties of Ce, Dy Doped ZnB₂O₄ Phosphor

Kamlesh Thakkar — 2026-01-28

Samples of Ce³⁺ and Dy³⁺ doped Zinc Borate (ZnB₂O₄) phosphors were synthesized using the solid-state reaction method. Structural characterization was performed using X-Ray Diffraction (XRD), surface morphology was analyzed by Field-Emission Scanning Electron Microscopy (FESEM), and elemental composition was determined via Energy Dispersive Spectroscopy (EDS). The XRD pattern of the synthesized sample closely matches the JCPDS 39-1126 reference. Thermoluminescence (TL) analysis revealed that the samples doped with 2 mol% Ce³⁺ and Dy³⁺ exhibit the highest TL intensity. Upon irradiation of both samples with varying Ultraviolet (UV) exposure times, the maximum TL intensity was observed with a 15-minute UV dose. Trapping parameters were calculated using Chen’s method, and the relationship between total TL intensity and UV dose, as well as the TL emission spectra, were also recorded.

Optimization of Cascaded Raman Stokes Generation Using Effective Area Variations in Optical Fibers

Angeles Yolanda Pages-Pacheco — 2026-01-28

By introducing discontinuities in the effective area of the optical fiber through the splicing of a short fiber segment, the performance of a cascaded Raman laser system has been significantly improved. By incorporating a 46 cm thin-core Nufern 980HP fiber between two spans of larger-core Corning MetroCor fiber, we achieved enhanced output power and conversion efficiencies for the Stokes signals. Specifically, conversion efficiency improvements of ∼ 26.20%, ∼39.21%, and ∼ 82% were observed for the 2nd, 3rd, and 4th Stokes, respectively. Additionally, the Raman threshold was reduced, resulting in a pumping power requirement reduction of ∼ 14.8% and ∼ 13.6% for the 2nd and 3rd Stokes. Our results confirm that this simple and cost-effective approach enables significant improvements in Raman gain medium performance, offering new pathways for energy-efficient Raman fiber lasers for applications in Medicine, spectroscopy, biomedical imaging, remote sensing, and Telecomm.

Optical Absorption of Aluminum Nanoparticles

Νikolaos T. Ntelis — 2026-01-28

In this study, the optical absorption properties of small Aluminum (Al) nanoparticles were systematically investigated by using Density Functional Theory (DFT) calculations. A series of nanostructures ranging from Al₄ to Al₂₄ was modeled and optimized using the Perdew, Burke, and Ernzerhof (PBE0) functional and def2-TZVP basis set. The resulting absorption spectra revealed that both the position and intensity of the first and highest absorption peaks depend strongly on the size and geometry of the clusters. A gradual redshift of the first absorption peak was observed as the number of atoms increased, transitioning from the Ultraviolet (UV) to the visible and eventually to the Near-Infrared (NIR) region of the electromagnetic spectrum. The Al₅ cluster exhibited the most favorable first peak in the UV region, which was calculated at 3.90 eV, Al₈ in the visible, which was calculated at 2.47 eV, and Al₁₂ in the NIR, calculated at 1.51 eV. Similarly, the highest absorption peak transitioned from the UV for Al₄, calculated at 4.66 eV, to the visible region for Al₁₃, which was found at 2.83 eV with increasing cluster size. The binding energy calculations indicated increasing structural stability with size, peaking at 2.70 eV for the Al₂₃ cluster. These findings confirm the high tunability of the optical properties of Al nanoclusters and underscore their potential in plasmonic applications across the Ultraviolet Visible (UV-Vis)-NIR spectrum. Given aluminum’s low cost, abundance, and strong light-matter interaction, this group of nanoparticles emerges as a promising alternative to noble metals and copper for a wide range of nanophotonic and plasmonic technologies.