Optical Effects Research Articles

Spin‐Orbit Torque Switching of Magnetization in Ultra‐Thick Ferromagnetic Layers

AbstractCurrent‐induced magnetization switching via spin‐orbit torque (SOT) holds great potential for applications in high‐speed and energy‐efficient magnetic memory and logic devices. In the extensively studied heavy metal/ferromagnet (HM/FM) SOT heterostructures, the thickness of the FM layer is typically restricted to a few nanometers or less due to the rapid spin dephasing, making it challenging to implement thermally stable memory cells with high density. In this study, it is demonstrated that this thickness constraint can be significantly alleviated by utilizing an oxide ferromagnet La0.67Sr0.33MnO3 (LSMO). Through electrical transport and magnetic optical measurements, it is found that the SOT can switch the magnetization in Pt/LSMO heterostructures even at an LSMO thickness of 35 nm, which is one order of magnitude larger than that for metallic FMs, such as CoFeB. Furthermore, based on the FM thickness dependence of the switching current and the domain switching type revealed by magnetic optical Kerr effect imaging (MOKE), a possible picture is proposed to describe the SOT switching in Pt/LSMO, which highlights the critical role of the domain wall propagation in the vertical direction. The work provides valuable insights into the behavior of SOT switching in ultra‐thick FM films, offering new possibilities for their practical applications.

Rotating target detection model under arbitrary incidence of the vortex beam based on optical RDE

Abstract The optical rotational Doppler effect (RDE) related to orbital angular momentum has attracted extensive attention in rotating targets detection. In this paper, we present a novel rotating target detection model based on optical RDE, where the vortex beam can be incident on the rotating target with an arbitrary case. Based on the proposed detection model, we investigated the mechanism of rotation Doppler shift and deduced the generalized formula of the Doppler frequency shift under arbitrary incidence of the vortex beam by phase modulation method. Subsequently, the model is studied under different incidence conditions, and the variation of Doppler frequency shift with different incident parameters is analyzed combining with the deduced formulas. Meanwhile, we also give the detection methods to for motion parameter estimations of the rotating target. Theoretical and simulated results verify the effectiveness of the proposed model, and more detailed motion parameters can be obtained based on RDE. This theoretical model enables us to better understand the generation of the rotational Doppler frequency and may be useful for the application of remote sensing of a rotating target.

Nonlinear Optical Effects of Hybrid Antimony(III) Halides Induced by Stereoactive 5s2 Lone Pairs and Trimethylammonium Cations.

Organic-inorganic hybrid metal halides have unique optical and electronic properties, which are advantageous in the study of nonlinear optical materials. To investigate the effect of stereoactive lone pair electrons and the induction of organic cations on the structure of hybrid antimony(III) halides on nonlinear optics, we synthesize two noncentrosymmetric hybrid antimony(III)-based halide single crystals (TMA)3Sb2X9 (TMA = NH(CH3)3+, X = Cl, Br) by a room-temperature slow evaporation method, and their single-crystal structures, phase transition, X-ray photoelectron spectroscopy, and energy-band structure calculations are studied. More importantly, second-harmonic generation results of (TMA)3Sb2X9 (X = Cl, Br) are about 0.7 and 0.8 × KH2PO4(KDP), respectively. Interestingly, (TMA)3Sb2Cl9 single crystals undergo a reversible structural transition from Pc (No. 7) at room temperature to P21/c (No. 14) at 400 K, while the (TMA)3Sb2Br9 single crystals belong to the noncentrosymmetric space group R3c (No. 161), which clarifies the previous results. This work not only deepens the understanding of the role in lone pair electrons and organic cations in the structural induction in antimony-based halide perovskite materials but also provides guidance for subsequent nonlinear optical explorations.

Large‐Scale Bottom‐Up Fabricated 3D Nonlinear Photonic Crystals

Nonlinear optical effects are used to generate coherent light at wavelengths difficult to reach with lasers. Materials periodically poled or nanostructured in the nonlinear susceptibility in three spatial directions are called 3D nonlinear photonic crystals (NPhCs). They enable enhanced nonlinear optical conversion efficiencies, emission control, and simultaneous generation of nonlinear wavelengths. The chemical inertness of efficient second‐order nonlinear materials () prohibits their nanofabrication until 2018. The current methods are restricted to top‐down laser‐based techniques limiting the periodicity along the z‐axis to . The first bottom‐up fabricated 3D NPhC is demonstrated in sol–gel‐derived barium titanate by soft‐nanoimprint lithography: a woodpile with eight layers and periodicities of (‐plane) and (z‐plane). The surface areas exceed , which is two orders of magnitude larger than the state‐of‐the‐art. This study is expected to initiate bottom‐up fabrication of 3D NPhCs with a supremely strong and versatile nonlinear response.

Research on the optical properties and effect of the transparent epoxy for the JUNO central detector

The Central Detector (CD) of the Jiangmen Underground Neutrino Observatory (JUNO) has a large acrylic sphere containing 20,000 tons of liquid scintillator (LS) and is immersed in high purity water. The CD consists of 263 acrylic spherical panels and two chimneys, which are bonded together by mass polymerization. Transmittance and stress are critical factors for the CD, with transmittance affecting JUNO's energy resolution and stress affecting the structural integrity of the detector. The bonding areas of the CD are of particular concern, leading to the development of specialized measurement systems for acrylic stress and transmittance. Stress measurements revealed the presence of higher than expected levels of stress in the bonding areas, requiring assessments and protective measures. The application of a transparent epoxy on the bonding areas was proposed as an effective structural protection measure, although it may reduce the transmittance of these areas. Consequently, the optical properties of the transparent epoxy, such as refractive index and absorbance at 420 nm, were studied using acrylic samples to analyze the effect of the epoxy application on the transmittance performance of the CD. These results are detailed and discussed in this article.

High-precision spatiotemporal three-dimensional ultrashort pulse synchronization with optical Kerr effect

In studying the interaction of multiple ultrashort pulses with matter, high requirements are put forward for spatiotemporal synchronization accuracy. Limited by the response time and bandwidth of existing devices, the synchronization of multiple ultrashort pulses still faces significant difficulties. By observing the transient phenomena of the optical Kerr effect, high-precision, three-dimensional (x, y, t) synchronization of ultrashort pulses at different angles was achieved. In the optical Kerr effect, the polarization state of the signal pulse changes only when it coincides with the pump pulse, at which point the signal pulse passes through the analyzer. The changes in the intensity and phase of the signal pulse is positively correlated with the degree of spatiotemporal coincidence. In this study, 10-ps pulses were used in the experiments. By observing the intensity and phase distribution of the signal pulses, a time synchronization accuracy between two pulses of less than 1 ps and spatial synchronization accuracy of ±125 µm and ±3 µm in the x and y directions, respectively, were achieved. Moreover, the synchronization of two pulses at an angle of 90 ° was measured, further proving that the method can achieve the spatiotemporal synchronization of pulses with large angles. Therefore, this method has important application prospects in the study of multi-beam interactions with matter and other ultrafast physical phenomena.

Broadband and ascendant nonlinear optical properties of the wide bandgap material GaN nanowires

Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10−4 cm3/GW2. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm2, 5.58 GW/cm2 and 14.13 GW/cm2. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.

Performance evaluation and investigation of diffraction optical elements effect on bit error rate of free space optics and performance investigation of space uplink wireless optical communication under varying atmospheric turbulence conditions

AbstractSeveral other optical antenna topologies have been developed and implemented throughout the years. These topologies include a variety of optical components, including the axicon optical element, dual‐secondary mirror, cone reflecting mirror, prism beam slier, and beam‐splitter/beam combiner. In contrast, the secondary reflecting mirror causes an obscuration loss that must be compensated for by reducing the transmission power in an optical antenna design. In order to address this issue in space optical communication, the present research helps to develop an enhanced two diffractive optical elements (DOEs) technology however the data presented therein only shows that DOEs may boost transmission power efficiency, which is insufficient for system designers. Though On‐Off Keying (OOK) is widely used in optical communication systems at the moment, the proposed research include DOEs into an OOK space uplink optical. The proposed research uses numerical simulation to explore how much a space uplink OOK system's bit error rate (BER) may be improved by using DOEs and adjusting fundamental parameters. The proposed BER model takes environmental factors like wind and detector noise into account. Using this theoretical model, the present work helps to investigate the effect of DOEs on the BER versus fundamental parameter characteristic curves in space uplink optical communication. Based on the findings, the DOEs structure has the potential to significantly enhance the BER performance of space uplink optical communication systems, especially at high obscuration ratios. When the obscuration ratio is 0.25, 0.167, or 0.125 and the transmission power is 1 W, for instance, the DOEs may improve the BER by a factor of two or one order of magnitude or less when the parameters are changed to the typical parameter values as specified. Results increase by a factor of six, three, and two orders of magnitude, respectively, when transmitting at 5 W. The results show that DOEs can significantly enhance the BER performance, especially at high obscuration ratios. The findings suggest that integrating DOEs into the optical subsystem is a straightforward approach to improving the performance of space uplink optical communication systems.

Abundant New Optical Soliton Solutions to the Biswas–Milovic Equation with Sensitivity Analysis for Optimization

This study extensively explores the Biswas–Milovic equation (BME) with Kerr and power law nonlinearity to extract the unique characteristics of optical soliton solutions. These optical soliton solutions have different applications in the field of precision in optical switching, applications in waveguide design, exploration of nonlinear optical effects, imaging precision, reduced intensity fluctuations, suitability for optical signal processing in optical physics, etc. Through the powerful (G′/G, 1/G)-expansion analytical method, a variety of soliton solutions are expressed in three distinct forms: trigonometric, hyperbolic, and rational expressions. Rigorous validation using Mathematica software ensures precision, while dynamic visual representations vividly portray various soliton patterns such as kink, anti-kink, singular soliton, hyperbolic, dark soliton, and periodic bright soliton solutions. Indeed, a sensitivity analysis was conducted to assess how changes in parameters affect the exact solutions, aiding in the understanding of system behavior and informing decision-making, especially in accurately designing or analyzing real-world optical phenomena. This investigation reveals the significant influence of parameters λ, τ, c, B, and Κ on the precise solutions in Kerr and power law nonlinearities within the BME. Notably, parameter λ exhibits consistently high sensitivity across all scenarios, while parameters τ and c demonstrate pronounced sensitivity in scenario III. The outcomes derived from this method are distinctive and carry significant implications for the dynamics of optical fibers and wave phenomena across various optical systems.

Angle-Multiplexed 3D Photonic Superstructures with Multi-Directional Switchable Structural Color for Information Transformation, Storage, and Encryption.

Creating photonic crystals that can integrate and switch between multiple structural color images will greatly advance their utility in dynamic information transformation, high-capacity storage, and advanced encryption, but has proven to be highly challenging. Here, it is reported that by programmably integrating newly developed 1D quasi-periodic folding structures into a 3D photonic crystal, the generated photonic superstructure exhibits distinctive optical effects that combine independently manipulatable specular and anisotropic diffuse reflections within a versatile protein-based platform, thus creating different optical channels for structural color imaging. The polymorphic transition of the protein format allows for the facile modulation of both folding patterns and photonic lattices and, therefore, the superstructure's spectral response within each channel. The capacity to manipulate the structural assembly of the superstructure enables the programmable encoding of multiple independent patterns into a single system, which can be decoded by the simple adjustment of lighting directions. The multifunctional utility of the photonic platform is demonstrated in information processing, showcasing its ability to achieve multimode transformation of information codes, multi-code high-capacity storage, and high-level numerical information encryption. The present strategy opens new pathways for achieving multichannel transformable imaging, thereby facilitating the development of emerging information conversion, storage, and encryption media using photonic crystals.

Optical Third Harmonic Generation of Spherical Quantum Dots under Inversely Quadratic Hellmann Plus Inversely Quadratic Potential

Abstract The third harmonic generation (THG) coefficient for the spherical quantum dot (QD) system with Inversely Quadratic Hellmann Plus Inversely Quadratic Potential (IQHIQP) is investigated theoretically, considering the regulation of the quantum size, confinement potential depth and external environment. The numerical simulation results indicate that the THG coefficient can reach the order of 10-12 m2/V2, which strongly relies on the tunable factor, with its resonant peak experiencing a red-shift or blue-shift. Interestingly, the effect of temperature on the THG coefficient in terms of peak location and size is consistent with the quantum dot radius but contrasts with the hydrostatic pressure. Thus, it is crucial to focus on the influence of internal and external parameters on nonlinear optical effects, and to implement the theory in practical experiments and the manufacture of optoelectronic devices.

Photonic Metamaterial‐Inspired Polarization Manipulating Devices on Etchless Thin Film Lithium Niobate Platform

AbstractPhotonic metamaterials interact with light at the micro–nano scale, enabling unprecedented optical manipulation capabilities, which play a key role in nonlinear optics, spin optics, negative index, and zero index materials. Recently, thin‐film lithium niobate on insulator (LNOI) has emerged as a promising platform for integrated photonics due to its unique material properties, including an excellent electro–optic effect, wide transparency window, and low waveguide losses. Metamaterial structures are promising for constructing novel integrated photonic circuit building blocks on LNOI as they can provide advantageous circuit functionality. In this work, as a proof of concept, high‐performance polarization manipulating devices including polarization splitter rotator (PSR), polarization rotator (PR), and polarizer are demonstrated using photonic metamaterials on the etchless LNOI platform by introducing a silicon nitride layer on the top of LNOI wafer as the loading material. In this way, full advantage of lithium niobate (LN) can be taken to achieve various high‐performance integrated photonic devices, while avoiding the etching of LN and simplifying the fabrication process greatly, which can bring bright prospects for achieving large‐scale lithium niobate integrated photonic circuits.

Study of the Bunsen–Roscoe Reciprocity Law in Solar Water Disinfection (Optical Effect) for E. coli, E. faecalis and C. perfringens

Water stress and water quality represent major environmental challenges in the 21st century. In response, wastewater management and its potential reuse emerge as strategies to mitigate these problems. This research aims to verify the law of reciprocity in the solar disinfection process of real secondary wastewater effluents for different faecal microorganisms. Flat disinfection reactors, subjected only to natural and continuous UV radiation, were used. The study focused on the optical effect of UV radiation, eliminating the significant influence of the thermal effect and its synergy in solar disinfection at temperatures above 45 °C, by controlling the temperatures of the water samples to levels below 20 °C. Three experimental tests were carried out on sunny days. Each test comprised two trials, under the following conditions: (a) low solar irradiance over a prolonged time (duration approximately: 2.6 h) and (b) high solar irradiance and a shorter period of time (approximately 2 h), with each receiving the same UV dose. Inactivation kinetics was analysed for E. coli, E. faecalis, and C. perfringens (including spores). The results validated the reciprocity law for E. coli in all tests for UV doses > 20 Wh/m2, showing no significant deviations, with inactivation rates of 0.44 to 0.51 m2/Wh for initial concentrations of 106–107 CFU/100 mL. In contrast, for E. faecalis, the reciprocity was only valid at intensities < 700 W/m2, with rates of 0.04 and 0.035 m2/Wh for 105–106 CFU/100 mL; above this irradiance value, the law varied significantly and was not valid. C. perfringens did not show significant disinfection results during the experiments to verify this law, mainly due to the resistance of its spores. Additional experimentation with C. perfringens is necessary, by extending the length of the experiments and/or conducting them at higher irradiance values, in order to reach bacterial inactivation to enable the analysis of the reciprocity law. In general, the main conclusion from these results is that the reciprocity law in solar disinfection would be difficult to use for the estimation of water solar disinfection based on the irradiance and exposure times, as there are deviations from it at least in one specie (E. faecalis). Mores studies should be carried out to fully understand and determine the validity of this law and its potential application for forecasting solar water disinfection.

Optical vectorial-mode parity Hall effect: a case study with cylindrical vector beams

The vectorial optical field (VOF) assumes a pivotal role in light-matter interactions. Beyond its inherent polarization topology, the VOF also encompasses an intrinsic degree of freedom associated with parity (even or odd), corresponding to a pair of degenerate orthogonal modes. However, previous research has not delved into the simultaneous manipulation of both even and odd parities. In this study, we introduce and validate the previously unexplored parity Hall effect for vectorial modes using a metasurface design. Our focus lies on a cylindrical vector beam (CVB) as a representative case. Through the tailored metasurface, we effectively separate two degenerate CVBs with distinct parities in divergent directions, akin to the observed spin states split in the spin Hall effect. Additionally, we provide experimental evidence showcasing the capabilities of this effect in multi-order CVB demultiplexing and parity-demultiplexed CVB-encoded holography. This effect unveils promising opportunities for various applications, including optical communication and imaging.

Ultrafast Dynamics of Strong Near‐Field Coupled Localized and Delocalized Surface Plasmons

AbstractThis paper reports transient dynamics of strong near‐field coupling behavior of plasmons in a multilayer metal nanostructure that enables ultrahigh‐efficient optical switching. Particle plasmon on the top array units couples with localized/delocalized plasmons on the bottom Au film to produce dipolar and high‐order hybrid modes with nearly suppressed reflection. The mode coupling can be tuned from near‐field to far‐field regime readily mediated by the spacer thickness. The dipolar mode inherits the high dispersive property of the delocalized plasmon, but the higher‐order one shows limited dispersion. Transient spectroscopy illustrates both hybrid modes have a picosecond timescale redshift under on‐ and off‐resonance excitation. However, the higher‐order mode exhibits a longer decay lifetime than the dipolar one because of resonance characteristics and cavity properties. An ultrafast optical switching effect with a response time of τ = 3.2 ps and an ultrahigh efficiency of 5100 mOD mJ−1 cm2 is achieved under an extremely low pump fluence.

Optical injection effects in electrically pumped semiconductor nano-laser arrays

A theoretical analysis is performed on the response of electrically pumped nano-laser arrays to external optical injection. The response to both continuous wave and modulated optical injection is explored. Continuous wave injection is shown to excite several varieties of dynamical behaviour in the array elements including regular dynamics and quasi-periodic behaviour. The strength of the optical injection, the frequency detuning between the injected light and the target laser, and the magnitude of the Purcell spontaneous emission enhancement factor are shown to markedly affect the dynamics. When subject to modulated optical injection, the effects of frequency detuning and optical injection strength are the focus of attention. It is shown that the elements of the array subject to modulated optical injection exhibit oscillatory behaviour over broad regimes determined by the optical injection strength and the frequency detuning.

DNA Origami‐Directed Self‐Assembly of Gold Nanospheres for Plasmonic Metasurfaces

AbstractPlasmonic nanostructures are frequently utilized to create metasurfaces with a large variety of optical effects. Control over shape and positioning of the nanostructures is key to the function of such plasmonic metasurfaces. Next to lithographic means, directed self‐assembly is a viable route to create plasmonic structures on surfaces with the necessary precision. Here, a combined approach of DNA origami self‐assembly and electron beam lithography is presented for determinate positioning of gold nanospheres on a SiO2 surface. First, DNA origami structures bind to the electron beam‐patterned substrate and subsequently, gold nanoparticles attach to a defined binding site on the DNA origami structure via DNA hybridization. A sol‐gel reaction is then used to grow a silica layer around the DNA, thereby increasing the stability of the self‐assembled metasurface. A mean yield of 74% of single gold nanospheres is achieved located at the determinate positions with a spatial position accuracy of 9 nm. Gold nanosphere dimers and trimers are achieved with a rate of 65% and 60%, respectively. The applicability of this structuring method is demonstrated by the fabrication of metasurfaces whose optical response can be tuned by the polarization of the incoming and the scattered light.

From layer to building: Multiscale modeling of thermo-optical properties in 3D-printed facades

The challenge of building sector decarbonization has driven an integral rethinking of the way we design and build facades. Recently, large scale 3D-printing has emerged as an alternative manufacturing technique for novel facade components aiming at high operational efficiency and low environmental impact. Focusing on translucent polymer 3DPFs, this study tackles the challenges of modeling thermal and optical effects in geometrically complex components where interactions across multiple domains and scales occur. In particular, we introduce a novel method for modeling the irregular thermo-optical properties of 3DPFs, capable of capturing relevant effects often out of the scope of traditional modeling approaches. Our model accounts for geometry-dependent physical effects ranging from millimeter-scale fabrication details that impact optical behavior to centimeter-scale geometric features influencing heat and radiation transfer, extending up to the meter-scale implications for the building application. By employing computational techniques such as ray-tracing, computational fluid dynamics, and finite element analysis, we establish a model that offers detailed thermal and optical analysis to support performance-driven design iterations. Finally, demonstrating this approach in an office building context, we show that 3DPFs can match the performance of double glazing with dynamic shading, providing effective solar and thermal management over the year. This is achieved in a single, mono-material component with no active control, suggesting 3DPFs are a promising direction for low-environmental impact facade design.

Programmable Colloids with Analogous Hypercoordination Complex Architectures.

Colloidal molecule clusters (CMCs) are promising building blocks with molecule-like symmetry, offering exceptional synergistic properties for applications in plasmonics and catalysis. Traditional CMC fabrication has been limited to simple molecule-like structures utilizing isotropic particles. Here, we employ molecular dynamics simulation to investigate the co-assembly of anisotropic nanorods (NRs) and the stimulus-responsive polymer (SRP) via reversible adsorption. The results of the simulation show that it is possible to fabricate hypercoordination complex structures with high symmetry from the co-assembly of NRs and the SRP, even in analogy to the Th(BH4)4 structure. The coordination number of these CMCs can be precisely programmed by adjusting the shape and size of the ends of the NRs and the SRP cohesion energy. Furthermore, a finite-difference time-domain simulation indicates these hypercoordination structures exhibit significantly enhanced optical activity and plasmonic coupling effects. These findings introduce a new design approach for complex molecule-like structures utilizing anisotropic nanoparticles and may expand the applications of CMCs in photonics.

Analyzing the time-fractional (3 + 1)-dimensional nonlinear Schrödinger equation: a new Kudryashov approach and optical solutions

The paper focuses on investigating the time-fractional (3 + 1)-dimensional cubic and quantic nonlinear Schrödinger equation. We adopt the novel Kudryashov method to generate a distinct class of optical solutions for the current conformable fractional derivative problem. Our method explores various solution forms, including dark, wave, mixed dark-bright, and singular solutions. The soliton solutions we construct are visually represented to illustrate the influence of the fractional order derivative. Further, we elucidate the influence of solution parameters on the wave envelope, providing clear interpretations through 2D graphics presentations. The results underscore the efficacy of our approach in discovering exact solutions for nonlinear partial differential equations, especially in cases where alternative methods prove ineffective. The significance of the present paper lies in its contribution to advancing the understanding of the behavior of optical solutions in nonlinear systems, providing valuable insights for both theoretical and practical applications. In the field of nonlinear optics, this equation can describe the propagation of optical pulses in nonlinear media. It helps in understanding the behavior of intense laser beams as they propagate through materials exhibiting nonlinear optical effects such as self-focusing, self-phase modulation, and optical solitons.