Hasil untuk "Applied optics. Photonics"

Nanxi Li, C. Ho, J. Xue et al.

Light detection and ranging (LiDAR) sensors enable precision sensing of an object in 3D. LiDAR technology is widely used in metrology, environment monitoring, archaeology, and robotics. It also shows high potential to be applied in autonomous driving. In traditional LiDAR sensors, mechanical rotator is used for optical beam scanning, which brings about limitations on their reliability, size, and cost. These limitations can be overcome by a more compact solid‐state solution. Solid‐state LiDAR sensors are commonly categorized into the following three types: flash‐based LiDAR, microelectromechanical system (MEMS)‐based LiDAR, and optical phased array (OPA)‐based LiDAR. Furthermore, advanced optics technology enables novel nanophotonics‐based devices with high potential and superior advantages to be utilized in a LiDAR sensor. In this review, LiDAR sensor principles are introduced, including three commonly used sensing schemes: pulsed time of flight (TOF), amplitude‐modulated continuous wave TOF, and frequency‐modulated continuous wave. Recent advances in conventional solid‐state LiDAR sensors are summarized and presented, including flash‐based LiDAR, MEMS‐based LiDAR, and OPA‐based LiDAR. The recent progress on emerging nanophotonics‐based LiDAR sensors is also covered. A summary is made and the future outlook on advanced LiDAR sensors is provided.

A. Nemati, Qian Wang, M. Hong et al.

Metasurfaces, two-dimensional equivalents of metamaterials, are engineered surfaces consisting of deep subwavelength features that have full control of the electromagnetic waves. Metasurfaces are not only being applied to the current devices throughout the electromagnetic spectrum from microwave to optics but also inspiring many new thrilling applications such as programmable on-demand optics and photonics in future. In order to overcome the limits imposed by passive metasurfaces, extensive researches have been put on utilizing different materials and mechanisms to design active metasurfaces. In this paper, we review the recent progress in tunable and reconfigurable metasurfaces and metadevices through the different active materials deployed together with the different control mechanisms including electrical, thermal, optical, mechanical, and magnetic, and provide the perspective for their future development for applications.

M. H. Eisa, Ali Zia, Zainuriah Hassan et al.

Ultrafast laser two‐photon lithography (TPL) has revolutionized micro/nanofabrication, enabling the creation of intricate 3D structures with sub‐diffraction‐limited resolution. The integration of TPL with metasurface engineering has unlocked new frontiers in photonic device design, offering unprecedented control over light‐matter interactions at the nanoscale. This review delves into the cutting‐edge advancements in TPL as applied to the fabrication of metasurfaces, which are thin, artificially structured materials with unique optical properties. We explore TPL's unparalleled precision of TPL, which allows the creation of complex metasurface geometries, facilitating breakthroughs in diverse applications, including high‐efficiency diffractive optics, next‐generation imaging systems, quantum optics, and dynamic tunable photonic devices. Key challenges, such as material limitations, process optimization, and scalability, are discussed along with promising solutions and future directions for overcoming these barriers. Furthermore, the potential of TPL to drive innovation in areas such as optical sensing, energy harvesting, and quantum information processing is critically analyzed. Through this comprehensive review, we highlight the transformative role of ultrafast laser two‐photon lithography in advancing metasurface technologies, positioning it as a cornerstone of the future of photonics.

Gabriel Undeutsch, Maximilian Aigner, Ailton J Garcia et al.

Photon indistinguishability, entanglement, and antibunching are key ingredients in quantum optics and photonics. Decay cascades in quantum emitters offer a simple method to create entangled-photon-pairs with negligible multipair generation probability. However, the degree of indistinguishability of the photons emitted in a cascade is intrinsically limited by the lifetime ratio of the involved transitions. Here we show that, for the biexciton–exciton cascade in a quantum dot, this ratio can be widely tuned by an applied electric field. Hong-Ou-Mandel interference measurements of two subsequently emitted biexciton photons show that their indistinguishability increases with increasing field, following the theoretically predicted behavior. At the same time, the emission line width stays close to the transform-limit, favoring applications relying on the interference among photons emitted by different sources.

E. Zayed, M. Alngar, R. Shohib et al.

. The present paper derives highly dispersive soliton solutions in a coupler from optical metamaterials with Kerr law of nonlinear refractive index. In nonlinear optics and photonics, these wave packets possess a unique property, allowing them to sustain their shape and velocity during propagation through nonlinear media. Optical couplers utilizing metamaterials are advanced devices tailored to enhance the coupling and transfer of optical signals between different optical components or systems by harnessing the unique characteristics of these specially engineered materials. The paper's novelty lies in considering highly dispersive optical solitons that can be studied in optical couplers constructed from metamaterials. This paper’s primary goal is to integrate a governing model concerning highly dispersive solitons in optical couplers with the incorporation of metamaterials. Therefore, the unified Riccati equation expansion procedure and the enhanced Kudryashov’s scheme are adopted. They are being applied to such a device for the first time. These yield a full spectrum of optical solitons as well as straddled solitons. The novelty lies in the joint application of the two procedures, which uncovers various solitons. Furthermore, one of the approaches uncovers an unexpected benefit by revealing straddled soliton solutions.

A. Sánchez-Montes, Adrián Moya, E. Calzado et al.

Tunability of the retardance by liquid crystal on silicon microdisplays is at the heart of modern wavefront engineering in Optics and Photonics. However, a full knowledge of its dependence on voltage and illumination wavelength is not yet experimentally accessible. This would be very convenient, not only to set the optimal working conditions for applications, but also, on a more fundamental level, to explore the topology of the tunability of the phase retardance. The initial 2D nature of this parametric space increases in digital backplane devices, where the actual voltage depends on both the digital sequence addressed and on its low and high voltage values. Here, we demonstrate an efficient and accurate procedure to evaluate the absolute retardance across this multidimensional parametric space, which is given by applied voltage and wavelength, providing a novel and unprecedented insight.

Yinghao Cao, Yue Zhang, Wenlong Che et al.

Chalcogenide glasses are widely applied in the fields of infrared optics and nonlinear optics, which has spurred extensive research into their processing and fabrication, particularly for grating structures. We propose a novel method for fabricating grating structures in chalcogenide glass thin films utilizing their photobleaching effect via direct exposure, which is a physical process driven by light-induced oxidation and bond rearrangement. This phenomenon leads to localized changes in the refractive index, enabling the creation of high quality gratings. Two kinds of grating structure were fabricated which perform well in the diffraction effect. This method is easy to implement and cost-effective, making it ideal for large-scale production with promising applications, particularly in integrated photonics.

Zhenyue Chen, Yi Chen, Irmak Gezginer et al.

Abstract A critical gap currently exists in systematic understanding and experimental validation of the role of astrocytes in neurovascular coupling and their functional links with other brain cells. Despite a broad selection of functional neuroimaging tools for multi-scale brain interrogations, no methodology currently exists that can discern responses from neural and glial cells while simultaneously mapping the associated hemodynamic activity on a large scale. We present a hybrid multiplexed fluorescence and magnetic resonance imaging (HyFMRI) platform for measuring neuronal and astrocytic activity registered to concurrently recorded brain-wide hemodynamic responses. It features a fiberscope-based imaging system for multichannel fluorescence and optical intrinsic signal recordings and a custom surface radiofrequency coil, which are incorporated into the bore of a preclinical magnetic resonance imaging (MRI) scanner. We used HyFMRI to study peripheral-stimulus-evoked brain responses in mice differentially labeled with RCaMP and GCaMP genetically-encoded calcium indicators. Stimulation-evoked neuronal responses displayed the fastest kinetics and highest activation amplitude followed by astrocytic signals and the hemodynamic responses simultaneously recorded with functional MRI. In addition, the activation traces from neurons and astrocytes exhibited high linear correlation, thus providing direct evidence of astrocytic mediation in neurovascular coupling. This newly developed capacity to capture cell-type-specific calcium signaling alongside whole-brain hemodynamics enables the simultaneous investigation of neuro-glial-vascular interactions in health and disease. HyFMRI thus expands the current neuroimaging toolbox for a wide range of studies into synaptic plasticity, neural circuitry, brain function and disorders.

B. Tanduo, F. Matrone, A. Murtiyoso

Underwater photogrammetry presents unique challenges, including light attenuation, refraction, and turbidity, that affect the accuracy and quality of 3D reconstructions. This study investigates the performance of novel neural rendering techniques, Neural Radiance Fields (NeRF), SeaThru-NeRF, and 3D Gaussian Splatting (3DGS), in comparison to conventional Structure-from-Motion (SfM) workflows. Using a dataset acquired during the SIFET benchmark campaign on a submerged Roman archaeological site, we processed image data via Nerfacto, SeaThru, and Jawset Postshot (3DGS) and compared outputs against a reference model produced in Agisoft Metashape. Evaluation criteria included processing time, geometric accuracy (via M3C2 analysis), point cloud density and roughness, and point cloud completeness. Results show that radiance fields-based methods significantly reduce processing time while providing competitive visual results. SeaThru-NeRF demonstrated the highest geometric accuracy, benefiting from underwater-specific corrections, while 3DGS offered photorealistic rendering. These findings highlight the potential of neural methods for underwater cultural heritage documentation, though further improvements are needed in data fidelity and robustness under challenging underwater conditions.

On behalf of the organizing committee, we are delighted to present the proceedings of the Optics and Photonics in Africa Conference held on 6-10 November 2023 in White River, South Africa. This conference brought together researchers from around the globe to share their latest advancements, insights, and challenges in the field of Optics and Photonics. The conference featured a diverse program, including plenary and invited speakers, technical sessions for contributed talks, and poster presentations. These proceedings compile the contributions of the authors whose work was selected through a rigorous peer-review process. The papers in this volume cover a wide range of topics, including Applied Optics and Photonics, Biomedical optics, Fiber & Integrated Photonics, Green Photonics, Lasers & Light Sources, LIDAR and Photogrammetry, Light-matter Interaction, Nanophotonics, Nonlinear & Quantum Optics, Optical Instrumentation, Optical Metrology, Optical Materials, Photovoltaic Systems, Photonics for Aerospace and Spectroscopy. Each paper provides a unique perspective and contribution to advancing knowledge and innovation in the respective fields. We hope these proceedings will serve as a valuable resource for the scientific community, fostering further collaboration and research. We express our gratitude to the authors for their excellent contributions and to the reviewers for their time and expertise in ensuring the quality of the content. Our heartfelt thanks also go to the keynote speakers, session chairs, and sponsors, whose support and participation were essential to the success of this event. Finally, we would like to thank all participants for their enthusiasm and engagement, which made the Optics and Photonics in Africa a memorable and fruitful experience. We look forward to seeing you at future editions of this conference. Sincerely, The Editorial Team Dr Yaseera Ismail, Stellenbosch University, South Africa (Chair-OPA2023) Dr Christine Steenkamp, Stellenbosch University, South Africa Prof Malik Maaza, UNISA UNESCO Chair in Nanophotonics/iThemba Labs, South Africa

Ryan E. Dunagin, R. Mears, Dario Bueno-Baques et al.

Brillouin light scattering (BLS) is a powerful experimental tool that can be used to gain insights into the fundamental and applied properties of matter, like dispersions of quasiparticles in a solid, as well as their spatiotemporal dynamics. Many applications of light scattering favor the use of optical fibers in place of free-space optics. In this study, we compare the performance of anti-resonant hollow core fibers to that of conventional solid core fused silica fibers for BLS experiments in the GHz frequency range. Conventional fibers are barely suitable for low-noise measurements because of the spontaneous scattering of photons on various phononic modes present in the core and cladding. In the case of the hollow-core fiber, we identify a range of discrete phononic modes and associate them with the various acoustic modes of the structure surrounding the hollow core using finite-element numerical simulations. The measured relative intensity of the spontaneous BLS signal from these modes is orders of magnitude smaller than that of a solid-core fiber, making anti-resonant hollow-core fibers one of the best solutions for the single-mode light guidance for BLS and potentially other low-noise photonic experiments.

Pujing Zhang, Xue Hao, Qingli Zhou et al.

Mixed-dimensional van der Waals systems could improve terahertz modulators’ performance by utilizing the advantages of different dimensional materials. However, the reported available mixed-dimensional heterojunctions using two-dimensional (2D) and three-dimensional materials usually sacrifice the modulation speed to realize a higher modulation depth. Here, we creatively integrate one-dimensional (1D) nanowires with 2D nanofilms to construct the novel mixed-dimensional tellurium (Te) homojunction and achieve optimal indices with an ultrahigh modulation depth and a shorter carrier lifetime. In addition, a Te-based large-array imaging element was fabricated to successfully reproduce the painting colors under specific pump conditions as well as the dynamic multicolor display. Further measurements with the introduction of metamaterials prove that the required energy consumption can be significantly reduced by one order of magnitude. Our proposed 1D/2D integration strategy opens a new way to build high-performance terahertz functional devices and greatly expands the application fields of Te nanomaterials.

Lingmei Kong, Yun Luo, Qianqian Wu et al.

Abstract Light-emitting diodes (LEDs) based on perovskite semiconductor materials with tunable emission wavelength in visible light range as well as narrow linewidth are potential competitors among current light-emitting display technologies, but still suffer from severe instability driven by electric field. Here, we develop a stable, efficient and high-color purity hybrid LED with a tandem structure by combining the perovskite LED and the commercial organic LED technologies to accelerate the practical application of perovskites. Perovskite LED and organic LED with close photoluminescence peak are selected to maximize photon emission without photon reabsorption and to achieve the narrowed emission spectra. By designing an efficient interconnecting layer with p-type interface doping that provides good opto-electric coupling and reduces Joule heating, the resulting green emitting hybrid LED shows a narrow linewidth of around 30 nm, a peak luminance of over 176,000 cd m−2, a maximum external quantum efficiency of over 40%, and an operational half-lifetime of over 42,000 h.

J. P. Duque, M. A. Brovelli

The wide availability of geospatial data from different sources makes it necessary to create systems that are able to use and integrate the data to generate added value. We propose a system architecture following FAIR principles (Findable, Accessible, Interoperable, Reusable) and state-of-the-art methodologies for a server-side web-based application that performs virtual data integration over data sources that implement geospatial information standards. The architecture extends the mediator-wrapper design pattern with additional components that provide the system with additional flexibility and modularity, much needed for modern web applications. The architecture is composed of the mask, which acts as the interface of the system towards external users; a mediator that handles processing and data integration logic; a set of wrappers that communicate with the external data sources; persistent storage to provide flexible configuration and metadata capabilities to the system; and messaging queue for enabling asynchronous processing. At the same time, the architecture’s components are divided into four layers, each one with a specific role: presentation, configuration, processing, and communication.

Mohammed Elamassie, Murat Uysal

The deployment of non-terrestrial networks (NTNs) is envisioned to achieve global coverage for 6G and beyond. In addition to space nodes, aerial NTN nodes such as high-altitude platform stations (HAPSs) and rotary-wing unmanned aerial vehicles (UAVs) could be deployed, based on the intended coverage and operational altitude requirements. NTN nodes have the potential to support both wireless access and backhauling. While the onboard base station provides wireless access for the end users, the backhauling link connects the airborne/space-borne base station to the core network. With its high data transmission capability comparable to fiber optics and its ability to operate in the interference-free optical spectrum, free space optical (FSO) communication is ideally suited to backhauling requirements in NTNs. In this paper, we present a comprehensive tutorial on airborne FSO backhauling. We first delve into the fundamentals of FSO signal transmission and discuss aspects such as geometrical loss, atmospheric attenuation, turbulence-induced fading, and pointing errors, all of which are critical for determining received signal levels and related link budget calculations. Then, we discuss the requirements of airborne backhaul system architectures, based on use cases. While single-layer backhaul systems are sufficient for providing coverage in rural areas, multi-layer designs are typically required to establish connectivity in urban areas, where line of sight (LoS) links are harder to maintain. We review physical layer design principles for FSO-based airborne links, discussing both intensity modulation/direct detection (IM/DD) and coherent modulation/coherent demodulation (CM/CD). Another critical design criteria for airborne backhauling is self-sustainability, which is further discussed in our paper. We conclude the paper by discussing current challenges and future research directions. In this context, we discuss reconfigurable intelligent surfaces (RIS) and spatial division multiplexing (SDM), for improved performance and an extended transmission range. We emphasize the importance of advanced handover techniques and scalability issues for practical implementation. We also highlight the growing role of artificial intelligence/machine learning (AI/ML) and their potential applications in the design and optimization of future FSO-based NTNs.

Xiaoming Li, Liang Wang, Hang Zhang et al.

The discussion of resonance mechanisms for artificial structural units has always been a key to producing highly efficient, active and tunable meta-devices in the fields of controlling surface plasmon polaritons (SPPs) to generate surface plasmonic bending beams (SPBs). In this study, an array of 20 antisymmetric double V-shaped structures was designed to generate an SPB. The arms of the double V-shaped structures were panned to control the electric field intensity distributions of the SPB. The influence of the polarization states (such as polarization angles, linearly polarized (LP), left-circularly polarized (LCP) and right-circularly polarized (RCP) light) of the incident light on electric field intensity of SPB is discussed. These results can be well explained by the theory of dipole radiation. The numerical simulation results are in good agreement with the theoretical analysis. It is hoped that these results will help guide subsequent work in optimizing SPB generators.

Q. Ye, X. Zhang, X. Zhang et al.

Using images from UAV oblique ultra-long focal small view field whiskbroom camera (ULF-SVF-WC) system for object positioning and mapping is more difficult than conventional aerial photogrammetry, for the particularity of oblique ULF-SVF-WC imaging mode. Therefore, the precision and accuracy of its object positioning are also quite different from that of the conventional UAV photography. In this paper, we analysed the accuracy of real-time object positioning without ground control points (GCPs) for images from UAV oblique ULF-SVF-WC System. Firstly, we studied the imaging principles and characteristics of the oblique ULF-SVF-WC system. Then, we established the coordinate transformation relationship from the object point to the image point and constructed a strict imaging model for oblique ULF-SVF-WC image, which was used for real-time single-ray back-projection positioning assisted by DEM. Thirdly, we quantitatively analysed the distribution and variation of the oblique ULF-SVF-WC image single-ray back-projection errors in theory based on error propagation law and simulation data. Finally, we conducted the experiment of real oblique ULF-SVF-WC flight images for the actual positioning accuracy analysis. The experiment results showed that: the influence of system error on positioning generally conforms to the distribution and variation of theoretical precision, that is, the accuracy of scanning direction is much lower than that of the flight direction; while the accuracy of actual single-ray back-projection positioning is evidently lower than that of the theoretical analysis and there are obvious system errors in the positioning residuals. It indicates that the 6 external orientation elements calculated from POS data contains obvious system error whose influence is greater than random error and this should be eliminated in real-time single-ray back-projection for object positioning.

J. Gao, Y. Chen, Y. Guo et al.

For studies of urban development, it is an important method for obtaining the distribution of impervious surface (IS) areas and their dynamic change from remote sensing data. The dilemma of the same spectrum for different features and different spectrums for the same features, posed by the complexity of the IS objects, is the fundamental obstacle encountered in the extraction of urban IS areas. In this study, an automatic extraction method for urban IS areas is proposed and analyzed, based on classification and regression tree (CART) and ensemble learning strategies. The Sentinel-2 MSI data of 30 cities in China from 2018 to 2020 were selected for IS extraction experiments. We perform temporal and spatial modeling of the splitting threshold offset in the classification model to explore the effect of time and space on IS extraction. The obtained offset models show that the temporal variation is not significant, while the spatial offsets have more obvious linear relationships.

M. L. R. Lagahit, M. L. R. Lagahit, M. Matsuoka et al.

Road markings play an important role in vehicular navigation. It helps provide sufficient information for safe driving and smooth traffic flow. As such, with the rise of digital maps such as High-Definition (HD) maps, which are used by autonomous vehicles or self-driving cars, they must be well represented in their digital counterparts. However, survey-grade mobile mapping systems are expensive and thus open the idea of using lower-cost/level LIDAR sensors for mapping. Unfortunately, using such sensors provide sparser point clouds. This work aims to propose a method that successfully classifies road markings on sparse mobile LIDAR point cloud-derived images using UNET trained with focal loss. Results have shown successful road marking classification with a 94.68%increase in recall and a maximum 49.39% increase in F1-score. Adjusting precision by removing the insignificant class (“black”) further increases the resulting F1-score to 82.74%. Extending the method produces a classified point cloud by combining the classified image with a depth image. This research also aims to help aid boost the research on lower-cost/level sensors for mobile mapping purposes.

X. Xia, Z. Zhu, T. Zhang et al.

Satellite-derived aerosol optical depth (AOD) is an indispensable parameter when conducting studies related to atmospheric environment, climate change, and biogeochemical cycle. However, current satellite-derived AOD products are limited in related applications due to the large proportion of missing data, and the existed methods mainly concentrate on recovering AOD from polar-orbit satellite sensors. In order to solve these issues and take full use of the preponderance of geostationary satellite sensors in high frequency observation, we propose a spatiotemporal AOD recovery framework integrating multi-time scale AOD products based on the nested Bayesian maximum entropy methodology (NBME), aimed to obtain satellite-derived AOD datasets with low data missing and high accuracy. The experiment results show that the spatial coverage of AOD datasets increases from 20.5% to 70.0%, and the R² and RMSE of the recovered AOD against ground-based AERONET AOD are approximately 0.62 and 0.19, respectively. Moreover, the further simulated experiments indicate that the proposed method also performs better relatively when comparing with other popular recovery methods. Therefore, the proposed NBME recovery method can obtain a more convincing product both in applicable accuracy and visual quality.