Hasil untuk "Applied optics. Photonics"

K. Bliokh, F. J. Rodríguez-Fortuño, F. Nori et al.

This Review article provides an overview of the fundamental origins and important applications of the main spin–orbit interaction phenomena in modern optics that play a crucial role at subwavelength scales. Light carries both spin and orbital angular momentum. These dynamical properties are determined by the polarization and spatial degrees of freedom of light. Nano-optics, photonics and plasmonics tend to explore subwavelength scales and additional degrees of freedom of structured — that is, spatially inhomogeneous — optical fields. In such fields, spin and orbital properties become strongly coupled with each other. In this Review we cover the fundamental origins and important applications of the main spin–orbit interaction phenomena in optics. These include: spin-Hall effects in inhomogeneous media and at optical interfaces, spin-dependent effects in nonparaxial (focused or scattered) fields, spin-controlled shaping of light using anisotropic structured interfaces (metasurfaces) and robust spin-directional coupling via evanescent near fields. We show that spin–orbit interactions are inherent in all basic optical processes, and that they play a crucial role in modern optics.

Menghan Li, Kuan He, Zhiwen Ren et al.

The concepts of twistronics and magic angle have been widely applied beyond electrons, powering up new advancements in optics, acoustics, and heat transport. However, achieving a unidirectional or all-direction "magic angle" remains an established yet unresolved challenge in twisted bilayer metasurfaces across various disciplines. Our work proposes and validates a "twist-on-twist" paradigm to realizing unidirectional propagation and robust magic angle at arbitrary directions of the elastic out-of-plane wave. Our elastic metasurface not only exhibits a twisted configuration between the stacked bilayer but also significantly enhances out-of-plane symmetry breaking by further twisting meta-atoms in one constituent layer. Our twist-on-twist method unleashes versatile potentials of twisted thin composite materials to control the extreme propagation of topological elastic waves and even opens up new possibilities for photonic, phononic, and thermal moiré metamaterials.

Xinqin Liu, Pan Peng, Zhenyang Zhang et al.

Nanophotonic devices leverage unique interactions between photons and materials at the nanoscale, enabling applications in optical communication, biosensing, and quantum computing. These devices' properties are susceptible to material composition and structural design. Nanofabrication techniques, such as optical lithography, e‐beam lithography, two‐photon polymerization, and direct laser writing, have been widely applied to fabricate nanophotonic devices. Notably, rewritable fabrication stands out due to its low cost, flexibility, efficiency, and multi‐functionality. In this paper, a novel rewritable nanofabrication technique is proposed, which combines electrochemical reactions with direct laser writing, to fabricate nanophotonic devices on low‐cost indium tin oxide (ITO) films. The experimental results have demonstrated that high‐quality and erasable photonic structures such as diffraction gratings and holography masks can be directly fabricated using our technique. Hence, it is believed that this method can be applied in diverse fields such as nanophotonics, optoelectronic devices, biosensors, micro‐electromechanical systems, and nonlinear optics.

Jie Chang, Zhixia Xu, Shunli Li et al.

The quantum Hall effect arises when electrons in a two-dimensional plane are subjected to a magnetic field, causing them to undergo cyclotron motion and form discrete energy levels, known as Landau levels. These levels play a critical role in condensed matter physics. However, practical limitations of applying a magnetic field have led to the introduction of pseudomagnetic fields, which can similarly induce Landau levels. Such pseudomagnetic fields are typically generated through synthetic strain, achieved by deforming geometric patterns, and have been applied to systems like graphene, photons, and phonon crystals. Building on previous research in electronics and optics, we present a plasmonic metasurface that induces Landau levels via synthetic strain in the microwave frequency range. This strain is realized by printing metal structures of specific shapes on a dielectric substrate using printed circuit board technology. The fundamental unit of the plasmonic metasurface is a C6 symmetric structure composed of six localized surface plasmon patches. By applying a displacement function along the transmission direction, we discretize the dispersion curve, leading to band degeneration and the emergence of edge states. The distribution of these edge states is influenced by the strength of the pseudomagnetic field, which is controlled by the magnitude of the displacement function. We validate our design through fabricated models and demonstrate the existence of edge states using near-field scanning experiments. Our work, which combines synthetic magnetic fields and plasmonic metasurface, provides valuable insights for the development and application of integrated photonic devices.

Lei Wang, Hang Liu, Junwei Liu et al.

Abstract Bound states in the continuum (BICs) and exceptional points (EPs), as two distinct physical singularities represented by complex frequencies in non-Hermitian systems, have garnered significant attention and clear definitions in their respective fields in recent years. They share overlapping applications in areas such as high-sensitivity sensing and laser emission. However, the transition between the two, inspired by these intersections, remains largely unexplored. In this work, we reveal the transition process in a non-Hermitian two-mode system, evolving from one bound singularity to a two-dimensional exceptional ring, where the EP is the coalescent state of the quasi-Friedrich-Wintgen (FW)-BIC. This phenomenon is experimentally validated through pored dielectric metasurfaces in terahertz band. Furthermore, external pumping induced photocarriers as the dissipative perturbation, facilitates the breaking of degeneracy in the complex eigenfrequency and enables dynamic EP switching. Finally, we experimentally demonstrate a switchable terahertz beam deflection driven by the phase singularities of the EP. These findings are instrumental in advancing the development of compact devices for sensing and wavefront control within non-Hermitian systems.

Efim Khazanov

An analytical expression for focal intensity is derived for arbitrary surface profiles and arbitrary groove patterns of compressor gratings. The expression is valid for different compressor designs: plane and out-of-plane compressors, symmetric and asymmetric compressors (compressors composed by two not-identical pairs of gratings) and a two-grating compressor. It is shown that the quality requirements for the optics used to write a grating are higher than for the grating. The focal intensity can be maximized by rotating each grating around its normal by 180 degrees. Moreover, it may be increased to maximum by interchanging any two gratings in the compressor, because imperfections of an individual grating do not additively affect the focal intensity. The intensity decrease is proportional to the squared pulse spectrum width and the squared total distortions of the second and third gratings of the four-grating compressor and the total distortions of two gratings of the two-grating compressor.

I. M. Liubeka, K. V. Agarkov

Tellurium dioxide (TeO₂, paratellurite) remains a key material in photonics thanks to its high acousto-optic figure of merit, birefringence, and wide transparency. Devices based on TeO₂ - modulators, deflectors, and tunable filters - are widely used for beam control, spectral selection, and polarization. This review article examines in detail three major domains where TeO₂-based devices have become critical: space spectrometry, medicine, and quantum technologies. In space exploration, acousto-optic tunable filters (AOTFs) fabricated from TeO₂ are implemented in flagship instruments such as ESA’s NOMAD on ExoMars, NASA’s SuperCam on the Perseverance rover, and China’s Chang’e spectrometers. These instruments enable high-resolution, in spectral analyses of planetary surfaces and atmospheres, providing insights into mineralogy, volatiles, and habitability. In the medical domain, Acousto-optic frequency shifters (AOFS) and fiber-based laser Doppler vibrometers exploit TeO₂ to achieve precise, non-invasive measurements of middle ear ossicle vibrations, offering clinicians a novel diagnostic tool in otology. These systems, benefiting from the safety and versatility of telecom-band radiation, illustrate how AO devices can address unmet clinical needs. The translation of TeO₂-based devices into medicine highlights the interdisciplinary role of acousto-optics, bridging physics, engineering, and healthcare.Quantum technologies represent perhaps the most transformative frontier. Here, TeO₂-based acousto-optic modulators and deflectors are indispensable for photon-level control: fast frequency shifting, phase stabilization, routing, and generation of spatial modes of light. Their ability to integrate into bi-frequency interferometers and multi-channel quantum networks places them at the foundation of the emerging quantum internet, quantum communication protocols, and scalable quantum computing. Overall, such promising application areas require not only scaling up crystal production but also continuous improvement of their quality. The purpose of this review is to demonstrate concrete examples of how TeO₂ devices are applied across such diverse fields, underlining their continued importance for next-generation photonics.

Yang-Yang Wang, Nan Xue, Yunyun Wang et al.

Photon echo is a fundamental phenomenon that enables the coherent re-emission of a photon after a controlled delay, playing a crucial role in quantum information processing. Here, we propose a scheme for generating X-ray photon echoes via the dynamical control of collective nuclear excitation using an applied magnetic field. This mechanism facilitates the controllable exchange of nuclear coherence and the photonic field, enabling the on-demand generation of individual X-ray photons. Our scheme broadens the possibilities for realizing quantum qubits in the X-ray regime and advancing X-ray quantum optics.

Chuanshuo Wang, Chao Meng, Xianglong Mei et al.

Compared to conventional lasers limited to generating static modes, mode-switchable lasers equipped with adjustable optics significantly enhance the flexibility and versatility of coherent light sources. However, most current approaches to achieving mode-switchable lasers depend on conventional, i.e., inherently bulky and slow, optical components. Here, we demonstrate fiber lasers empowered by electrically actuated intracavity microelectromechanical system (MEMS)–based optical metasurface (MEMS-OMS) enabling mode switching between fundamental Gaussian and vortex modes at ~1030 nm. By finely adjusting the voltage applied to the MEMS mirror, high-contrast switching between Gaussian (l = 0) and vortex (l = 1, 2, 3, and 5, depending on the OMS arrangement) laser modes is achieved, featuring high mode purities (>95%) and fast responses (~100 microseconds). The proposed intracavity MEMS-OMS–enabled laser configuration provides an at-source solution for generating high-purity fast-switchable laser modes, with potential applications ranging from advanced optical imaging to optical tweezers, optical machining, and intelligent photonics.

Amirhossein Amjad, Xiaojun Xian

This review has explored optical sensors and their important role in non-invasive transdermal biomarker detection. While electrochemical sensors have been thoroughly studied for biomarker tracking, optical sensors present a compelling alternative due to their high sensitivity and selectivity, multiplex capabilities, cost-efficiency, and small form factor. This review examines the latest advancements in optical sensing technologies for transdermal biomarker detection, such as colorimetry, fluorescence, surface plasmon resonance (SPR), fiber optics, photonic crystals, and Raman spectroscopy. These technologies have been applied in the analysis of biomarkers present in sweat and skin gases, which are essential for non-invasive health monitoring. Furthermore, the review has discussed the challenges and future perspectives of optical sensors in in transdermal biomarker detection. The analysis of various sensor types and their applications highlights the transformative potential of optical sensors in enhancing disease diagnostics and promoting proactive health management.

Aofei Mao, Sarah Fess, Nada Kraiem et al.

Since 2001, 3D microfabrication based on two‐photon polymerization (TPP) has drawn extensive attention and interest in biology, optics, photonics, material science, and high‐energy physics. The in‐volume fabrication capability due to the threshold behavior of two‐photon absorption enables TPP higher flexibility compared with other nanofabrication techniques. However, as determined by the in‐volume fabrication feature as well as various reaction dynamics, the writing characteristics of TPP, such as throughput, accuracy, surface quality, and fabrication capability, are still limited. Herein, a comprehensive study is performed on the spatiotemporal behavior of reaction dynamics during TPP fabrication, mainly focusing on spatiotemporal characteristics of radical diffusion, photothermal effect, microscale mechanics, and voxel stacking process. Based on the study, a nonsequential fabrication method is established to simultaneously improve key writing characteristics of TPP and realize sharp features, high speeds, large overhang structure, and smooth surfaces. The method established in this work can be applied to improve the performance of functional devices for various fields.

Hongyang Wang, Yinyin Yan, Zijing Zhang et al.

In measuring object rotational velocity using vortex beam, the incident light on a tilted object causes spectral broadening, which significantly interferes with the identification of the true rotational Doppler shift (RDS) peak. We employed a velocity decomposition method to analyze the relationship between the spectral extremum and the central frequency shift caused by the object tilt. Compared with the linear growth trend observed when calculating the object rotational velocity using the frequency peak with the maximum amplitude, the central frequency calculation method effectively reduced the deviation rate of the RDS and velocity measurement value from the true value, even at large tilt angles. This approach increased the maximum tilt angle for a 1% relative error from 0.221 to 0.287 rad, representing a 29.9% improvement. When the tilt angle was 0.7 rad, the velocity measurement deviation reduction rate can reach 5.85%. Our work provides crucial support for achieving high-precision rotational velocity measurement of tilted object.

D. Skarlatos, B. Cuca, G. Kafataris et al.

This study explores low-cost photogrammetry solutions for surveying confined underground spaces, focusing on Tomb 7 at the UNESCO World Heritage Site, Tombs of the Kings in Paphos, Cyprus. The research, part of the ENGINEER project, compares traditional photogrammetric methods using frame cameras against a 360&deg; multi-lens camera. The aim is to identify reliable, low-cost methods for 3D documentation of archaeological sites, which can be used for structural analysis and systematic monitoring.<br />Three photogrammetric acquisition methodologies were tested: handheld with frame camera, standard with frame camera, and relaxed with 360&deg; camera. The study evaluates the accuracy of these acquisition methods by comparing dense point clouds generated from each dataset against a reference dataset obtained via terrestrial laser scanning (TLS). Metrics such as cloud-to-cloud distance, roughness, and point cloud density were used for comparison.<br />Results indicate that while the 360&deg; camera offers ease of use and high data density, it also introduces more noise and variability. Traditional methods, though more time-consuming, provide more consistent and accurate results. The findings suggest that combining both approaches could optimize data quality and acquisition efficiency, making the 360&deg; multi-lens camera a viable low-cost photogrammetry option for heritage documentation.

Yikai Wang, Boxia Yan, Mi Zhou et al.

We designed a narrow-linewidth external-cavity hybrid laser leveraging a silicon-on-insulator triple Euler gradient resonant ring. The laser’s outer cavity incorporates a compact, high-Q resonant ring with low loss. The straight waveguide part of the resonant ring adopts a width of 1.6 μm to ensure low loss transmission. The curved section is designed as an Euler gradient curved waveguide, which is beneficial for low loss and stable single-mode transmission. The design features an effective bending radius of only 26.35 μm, which significantly improves the compactness of the resonant ring and, in turn, reduces the overall footprint of the outer cavity chip. To bolster the laser power and cater to the varying shapes of semiconductor optical amplifier (SOA) spots, we designed a multi-tip edge coupler. Theoretical analysis indicates that this edge coupler can achieve an optical coupling efficiency of 85%. It also reveals that the edge coupler provides 3 dB vertical and horizontal alignment tolerances of 0.76 μm and 2.4 μm, respectively, for a spot with a beam waist radius of 1.98 μm × 0.99 μm. The outer cavity, designed with an Euler gradient micro-ring, can achieve a side-mode suppression ratio (SMSR) of 30 dB within a tuning range of 100 nm, with a round-trip loss of the entire cavity at 1.12 dB, and an expected theoretical laser linewidth of 300 Hz.

Tien Khee Ng, Alaaeddine Rjeb, Mitchell A. Cox et al.

A brief account of photonics research activities in the selected countries in the Middle East and Africa is presented in this article. Though not comprehensive, we hope to provide a glimpse of the research landscape in the region, and the collaboration and connection with each other and the international partners.

P. Clini, R. Nespeca, R. Angeloni et al.

This study evaluates the performance of three image-based 3D reconstruction methods&mdash;Structure-from-Motion with Multi-View Stereo (SfM-MVS), Neural Radiance Fields (NeRF), and Gaussian Splatting (GS)&mdash;for documenting Architectural Heritage (AH). Data acquisition was conducted using low-cost sensors: a drone to capture the stone portal of the external fa&ccedil;ade and a 360&deg; camera to document the interior spaces. NeRF and GS significantly outperformed SfM-MVS in processing time, with NeRF excelling in reconstruction completeness. However, GS faced challenges with point number control, and NeRF reconstructions exhibited artifacts and noise, particularly on flat surfaces. Accuracy assessments, using TLS point clouds as a benchmark, revealed that SfM-MVS provided the highest geometric precision for the external fa&ccedil;ade, despite minor gaps in reconstruction. In contrast, NeRF and GS fell short of the accuracy required for precise geometric documentation, with NeRF exhibiting prominent artifacts in flat or poorly detailed regions. Interior reconstructions were further limited by the higher Ground Sampling Distance (GSD) caused by the technical constraints of the 360&deg; camera and the increased capture distance for elevated areas. In conclusion, we can affirm that while NeRF and GS demonstrate strong potential for visualization due to their rendering quality and efficiency, SfM-MVS remains the most reliable method for achieving accurate geometric documentation of AH.

Dao Anh Vu, Nguyen Khoi Hoang Do, Huyen Ngoc Thi Nguyen et al.

In long-haul WDM (wavelength division multiplexing) optical communication systems utilizing the DP-16QAM modulation scheme, traditional methods for removing chaos have exhibited poor performance, resulting in a high bit error rate of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup></semantics></math></inline-formula> between the original signal and the removed chaos signal. To address this issue, we propose DeepChaos+, a machine learning-based approach for chaos removal in WDM transmission systems. Our framework comprises two key points: (1) DeepChaos+ automatically generates a dataset that accurately reflects the features of the original signals in the communication system, which eliminates the need for time-consuming data simulation, streamlining the process significantly; (2) it allows for the training of a lightweight model that provides fast prediction times while maintaining high accuracy. This allows for both efficient and reliable signal reconstruction. Through extensive experiments, we demonstrate that DeepChaos+ achieves accurate reconstruction of the original signal with a significantly reduced bit error rate of approximately <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></semantics></math></inline-formula>. Additionally, DeepChaos+ exhibits high efficiency in terms of processing time, facilitating fast and reliable signal reconstruction. Our results underscore the effectiveness of DeepChaos+ in removing chaos from WDM transmission systems. By enhancing the reliability and efficiency of chaotic secure channels in optical fiber communication systems, DeepChaos+ holds the potential to improve data transmission in high-speed networks.

T. Krauß

In this work we present a novel approach for segementation of a noisy DSM to building structures and other non-building structures &ndash; normally trees &ndash; and the modeling of them. Mostly Digital Surface Models (DSMs) from only a few aerial images or only from one pair of satellite images tend to be very noisy and lack good quality especially in shadow areas. Since actual methods for deriving roofs rely on a valid height information by joining areas of same slope to a roof-plane these fail regularly with such noisy DSMs. In our presented approach we use a slope map of the DSM only to detect flat regions. Since those regions on top of roofs are mostly good illuminated we can derive the ridges of roofs and flat roofs and also ground areas. All narrow, flat, elevated areas are ridges and may occur on roofs or on trees. After connecting ridges in ridge-directions there remain two types of ridges: long, straight ridges of roofs and mixed short ridges in many directions for the trees. Fitting symmetric planes through the roof-ridge-lines gives finally the roof-planes reducing the effects of noise on shadowed parts of the roof. Taking the other tree-ridges as seeds for a watershed transformation will give the trees. Finally the proposed method is applied to a noisy DSM and the results will be discussed.

Ren-Min Ma

Abstract Hyperbolic polariton vortices carrying reconfigurable topological charges have been realized at deep subwavelength scale.

M. Cannella

<p>In recent years research works have shown that augmented reality tools can offer effective support for the dissemination of architectural heritage, when integrated into the information data extracted with surveying and representation tools and further data from other sources, e.g., history.</p><p>The development and permanent updating of software platforms dedicated to augmented reality, i.e., Apple's ARKit and Google's ARCore, as well as the introduction of new features, offer today affordable support for the development of AR solutions.</p><p>Some operational difficulties are due to the rapid and constant evolution of the technologies; the available solutions can be compared to prototypes and the development of user experience effective solutions appears still lacking. The main subject in the construction of AR solutions is still linked to the development of effective methods to properly set up the visualization of 3D models and their interaction with the real scene. The chosen case study for the test of persistent AR solution for the visualization of works of art is the ‘Tribuna’, i.e., a monumental and sculptural marble apparatus, that decorated the main apse of the Cathedral of Palermo.</p>