Hasil untuk "Applied optics. Photonics"

J. Carolan, C. Harrold, Chris Sparrow et al.

Complex quantum optical circuitry Encoding and manipulating information in the states of single photons provides a potential platform for quantum computing and communication. Carolan et al. developed a reconfigurable integrated waveguide device fabricated in a glass chip (see the Perspective by Rohde and Dowling). The device allowed for universal linear optics transformations on six wave-guides using 15 integrated Mach-Zehnder interferometers, each of which was individually programmable. Functional performance in a number of applications in optics and quantum optics demonstrates the versatility of the device's reprogrammable architecture. Science, this issue p. 711; see also p. 696 A reconfigurable optical circuit provides a platform for a photonically-based quantum computer. [Also see Perspective by Rohde and Dowling] Linear optics underpins fundamental tests of quantum mechanics and quantum technologies. We demonstrate a single reprogrammable optical circuit that is sufficient to implement all possible linear optical protocols up to the size of that circuit. Our six-mode universal system consists of a cascade of 15 Mach-Zehnder interferometers with 30 thermo-optic phase shifters integrated into a single photonic chip that is electrically and optically interfaced for arbitrary setting of all phase shifters, input of up to six photons, and their measurement with a 12-single-photon detector system. We programmed this system to implement heralded quantum logic and entangling gates, boson sampling with verification tests, and six-dimensional complex Hadamards. We implemented 100 Haar random unitaries with an average fidelity of 0.999 ± 0.001. Our system can be rapidly reprogrammed to implement these and any other linear optical protocol, pointing the way to applications across fundamental science and quantum technologies.

P. Russell, P. Holzer, Wonkeun Chang et al.

Z. Vardeny, A. Nahata, A. Agrawal

Panaiot G. Zotev, Paul Bouteyre, Yadong Wang et al.

Hosna Sultana

The mid-wave infrared (MWIR) spectral range can provide a larger bandwidth for optical sensing and communication when the near-infrared band becomes congested. This range of thermal signatures can provide more information for digital imaging and object recognition, which can be unraveled from polarization-sensitive detection by integrating the metasurface of the subwavelength-scale structured interface to control light–matter interactions. To enforce the metasurface-enabled simultaneous detection and parallel analysis of polarization states in a compact footprint for 4-micron wavelength, we designed a high-contrast germanium metasurface with an axially asymmetric triangular nanoantenna with a height 0.525 times the working wavelength. First, we optimized linear polarization separation of a 52-degree angle with about 50% transmission efficiency, holding the meta-element aspect ratio within the 3.5–1.67 range. The transmission modulation in terms of periodicity and lattice resonance for the phase-gradient high-contrast dielectric metasurface in correlation with the scattering cross-section for both 1D and 2D cases has been discussed for reducing the aspect ratio to overcome the nanofabrication challenge. Furthermore, by employing the geometric phase, we achieved 40% and 60% transmission contrasts for the linear and circular polarization states, respectively, and reconstructed the Stokes vectors and output polarization states. Without any spatial multiplexing, this single metasurface unit cell can perform well in the division of focal plane Stokes thermal imaging, with an almost 10-degree field of view, and it has an excellent refractive index and height tolerance for nanofabrication.

L. Ferrari

Hazard mitigation and risk assessment for built heritage are central to contemporary conservation strategies, particularly in seismic-prone areas like Italy. This study presents preliminary findings of a research project focusing on the seismic vulnerability of historical masonry churches in the Province of Parma, a region with moderate seismic risk and a rich architectural heritage. Churches are among the most seismically vulnerable structures due to their complex construction, undocumented modifications, and sometimes ineffective past interventions. The research integrates GIS-based territorial analysis with archival investigation to evaluate the effectiveness of seismic strengthening measures implemented after the 1983 earthquake, especially in light of subsequent seismic events. A comprehensive database has been developed, cataloguing construction typologies, damage reports, and intervention strategies. Statistical and comparative analysis at both territorial and building scales helps assess the relationship between masonry characteristics, reinforcement techniques and seismic performance. Findings underscore the crucial role of past interventions in influencing current structural behaviour – sometimes positively, but also with unintended consequences. The study highlights the value of a multidisciplinary, data-driven approach combining digital tools and historical knowledge to support risk-informed conservation strategies. Ultimately, it aims to inform prioritization and planning frameworks that enhance the resilience of cultural heritage against future seismic events.

Seungmin Nam, Wontae Jung, Jun Hyuk Shin et al.

Abstract Wavelength-tunable structural colors using stimuli-responsive materials, such as chiral liquid crystals (CLCs), have attracted increasing attention owing to their high functionality in various tunable photonic applications. Ideally, on-demand omnidirectional wavelength control is highly desirable from the perspective of wavelength-tuning freedom. However, despite numerous previous research efforts on tunable CLC structural colors, only mono-directional wavelength tuning toward shorter wavelengths has been employed in most studies to date. In this study, we report the ideally desired omnidirectional wavelength control toward longer and shorter wavelengths with significantly improved tunability over a broadband wavelength range. By using areal expanding and contractive strain control of dielectric elastomer actuators (DEAs) with chiral liquid crystal elastomers (CLCEs), simultaneous and omnidirectional structural color-tuning control was achieved. This breakthrough in omnidirectional wavelength control enhances the achievable tuning freedom and versatility, making it applicable to a broad range of high-functional photonic applications.

Nikolaos A. Stathopoulos, Christos Lazakis, Iraklis Simos et al.

An easy-to-implement and cost-effective Fiber Bragg Grating (FBG) sensor interrogation technique based on a ring Erbium-Doped Fiber Laser (EDFL) topology is proposed and experimentally assessed. The FBG sensor is part of the EDFL cavity and must have a central wavelength located within the linear region of the EDF’s amplified spontaneous emission (ASE) spectrum, which occurs at between 1530 and 1540 nm. In this manner, the wavelength-encoded response of the FBG under strain is converted to a linear variation in the laser output power, removing the need for spectrum analysis as well as any limitations from the use of external edge-filtering components. In addition, the laser linewidth is significantly reduced with respect to the FBG bandwidth, thus improving the resolution of the system, whereas its sensitivity can be controlled through pumping power. The performance of the system has been characterized by modeling and experiments for EDFs with different lengths, doping concentrations, and pumping power levels. The influence of mode-hopping in the laser cavity on the resolution and accuracy of the system has also been investigated.

F. Galdames, P. González, F. Magni-Pérez et al.

The classification of tree species by remote sensing is an important task with a broad range of applications, including forest management, environmental monitoring, and climate change studies. Hyperspectral imaging has proven to be a valuable tool for this classification. Additionally, deep learning techniques have obtained outstanding results in hyperspectral classification. In this study, we apply a neural network to the classification of aerial hyperspectral images of trees. The study was conducted at a research station in southern Chile with 32 tree species. Our database has 3080 tree canopies that have been manually segmented and classified. The goal of the work was to study the correlation between forest structure complexity and classification performance across three different forest conditions: native forest, plantation of native species, and plantation of exotic species. The results show that classification performance is higher when forest structure and composition are simpler. We used a ResNet neural network as classifier and compared its performance with support vector machine and random forest. The best performance was obtained using ResNet in exotic plantations, the forest condition with the simplest structure, achieving an F1-score of 85.23%.

S. Falahatnejad, A. Karami

In this paper, a new classification technique for hyperspectral images (HSIs) based on an augmented active learning (AL) is introduced. The proposed method consists of two main steps: first, a 2-D non-subsampled shearlet transform (NSST) is applied to each spectral band of HSIs to extract the spatial features. After that, the kernel minimum noise fraction (KMNF) is used to reduce the spectral dimension. Second, the classification task using an augmented active learning technique is performed. For this purpose, an iterative process is considered. At each iteration, a discriminative sample selection and augmentation are used to create the training set. Then, the support vector machine (SVM) is iteratively applied to the training set. In the proposed method, the most informative samples are selected by a new query function combination of a posterior probability-based uncertainty and angle-based diversity criteria. The augmentation strategy during the training process is chosen by two-sample Kolmogorov-Smirnov test and the existing outliers are removed by k-means clustering. Finally, the proposed algorithm is applied to the real datasets and compared with three state-of-the-art AL algorithms. The obtained results show that the proposed method significantly increases accuracy considering the most informative samples.

A. Pifferi, D. Contini, A. D. Mora et al.

Abstract. The recent developments in time-domain diffuse optics that rely on physical concepts (e.g., time-gating and null distance) and advanced photonic components (e.g., vertical cavity source-emitting laser as light sources, single photon avalanche diode, and silicon photomultipliers as detectors, fast-gating circuits, and time-to-digital converters for acquisition) are focused. This study shows how these tools could lead on one hand to compact and wearable time-domain devices for point-of-care diagnostics down to the consumer level and on the other hand to powerful systems with exceptional depth penetration and sensitivity.

Lu Han, Zhan Li, Chao Chen et al.

Vector beams (VBs) have spatially inhomogeneous polarization states distribution and have been widely used in many fields. In this paper, we proposed a method to modulate polarization states of higher-order Poincaré (HOP) beams and designed a system based on Mach-Zehnder interferometers, in which polarization state (include azimuth and ellipticity) of generated HOP beams were modulated by linear electro-optic (EO) effect of nonlinear optical crystals. Using this method, the polarization state of generated HOP beams could be controlled by voltage signal applied on EO crystals, which makes the process of the polarization state change with no optical element moving and mechanical vibrations. Besides, due to the flexibility of the voltage signal, the polarization state could be switched directly and immediately.

A. Nega, V. Coors

<p>The relevance of 3D cadastre is increasing from time to time as buildings become more complex. Modeling and storing the physical structure with all its elements in a standardized file format improve its usability in different sectors, reduces data redundancy, creates data consistency, maintainability and scalability would be more effortless. In cadastre, showing the legal right of a property is as important as showing the physical right. Especially when a property is multiple owned and has several uses where each use and owner have different rights, responsibilities, and restrictions. The current cadastral of Addis Ababa is a 2D parcel-based mainly focused on registering ownership and physical data. The system lacks to show overlapping ownerships and uses of multistorey buildings. This study solved this critical short come.</p><p>The primary goal of this study was to use CityGML to represent the physical and non-physical boundaries of building units. Prior to the release of CityGML 3.0, CityGML 2.0 was widely utilized in this field. However, there are several legal boundary modeling flaws in CityGML 2.0. Contrarily, those gaps were closed in the revised edition. Because of this, CityGML 3.0 was used in this investigation. Firstly, a sample building model was created and tested to demonstrate the concept sample. Then, the concept was realized on a model of an actual condominium building from the study area, Addis Ababa. The findings of the study demonstrate how CityGML 3.0 may be utilized for various 3D cadastre applications, including modeling the legal and physical boundaries of buildings.</p>

Y. Ye, Y. Ye, Y. Tian et al.

Alpine glaciers are sensitive to changes in land surface temperature (LST), and measurements of the mass balance are limited, especially for small glaciers. In this study, we investigate the relationship between snow albedo of the melting season (June, July, and August) and annual glacier mass balance of the White Glacier from 2002 to 2018. Since there are many gaps in the albedo data, we use a interpolation method to fill them and then obtain the average value of the melting season. The study results show that surface temperature plays a dominant role in albedo and mass balance changes, and mass balance change and albedo variation show a significant consistency, with an excellent correlation (R²&thinsp;&gt;&thinsp;0.93). The acceleration of mass balance shows that the rate of mass reduction slows down, and the albedo change shows that the albedo increases from year to year. The interpolation albedo measurements using MODIS data can provide a useful means to reflect the annual change of glacier mass balance.

Michael John Fanous, Gabriel Popescu

In order to speed up the microscopy acquisition process, we developed a method, termed GANscan, in which videos are recorded as the stage is moving at high speeds. Using generative adversarial networks (GANs), we achieve 30x the throughput of stop-and-stare systems.

Liang Nie, Xiaonan Li, Hongwei Chen et al.

To solve the problem of low demodulation accuracy of conventional peak-to-peak algorithm for fiber-optic Fabry-Perot (FP) sensors due to failure of determining the interference order, a novel cavity length sequence matching demodulation algorithm based on a combined valley peak positioning is proposed. Firstly, a pair of a peak and its neighboring valley in the reflection spectrum is selected and positioned, and two groups of interference orders are supposed to generate two groups of cavity length sequences. Finally, these cavity lengths are compared to find the real interference order of the peak and valley for the extraction of the accurate cavity length. In order to verify the feasibility and performance of the proposed algorithm, simulations and experiments were carried out for fiber-optic FP sensors with cavity lengths in the range of 15–115 μm. A demodulation accuracy better than 8.8 nm was found. The proposed algorithm can achieve highly accurate cavity length demodulation of fiber-optic FP sensors.

Yiwei Sun, Xiaoyan Wu, Jianhong Shi et al.

Imaging objects hidden behind an opaque shelter provides a crucial advantage when physically going around the obstacle is impossible or dangerous. Previous methods have demonstrated that is possible to reconstruct the image of a target hidden from view. However, these methods enable the reconstruction by using the reflected light from a wall which may not be feasible in the wild. Compared with the wall, the “plug and play” scattering medium is more naturally and artificially accessible, such as smog and fogs. Here, we introduce a scattering-assisted technique that requires only a remarkably small block of single-shot speckle to perform transmission imaging around in-line-of-sight barriers. With the help of extra inserted scattering layers and a deep learning algorithm, the target hidden from view can be stably recovered while the directly uncovered view is reduced to 0.097% of the whole field of view, successfully removing the influence of large foreground occlusions. This scattering-assisted computational imaging has wide potential applications in real-life scenarios, such as covert imaging, resuming missions, and detecting hidden adversaries in real-time.

R. Kumar

Samar Emara, Taichiro Fukui, Kento Komatsu et al.

The optical-phased array (OPA) has gained special interest in recent years as a high-speed and compact imaging device. While large-scale OPAs have been demonstrated in single-pixel imaging, the complexity of the driver circuit is becoming a crucial problem as the number of phase shifters increases. Here, we investigate the phase shift requirement of OPA for single-pixel imaging and demonstrate, for the first time, that full 2&#x03C0; phase shifts are not mandatory to generate a set of illumination patterns with a sufficient degree of randomness required to reconstruct the image. Using a silicon photonic OPA chip with 128 carrier-depletion-based phase shifters, we experimentally confirm this property by successfully retrieving an image under a maximum phase shift of only &#x223C;1.5&#x03C0; without affecting the quality of the image. Consequently, the input voltage can be reduced significantly. Since the carrier-depletion phase shifters generally require high driving voltages, this finding paves the way to high-speed OPA-based imaging with a minimum device requirement.

M. Radulaski, M. Widmann, Matthias Niethammer et al.

We develop a scalable array of 4H-SiC nanopillars incorporating single silicon vacancy centers, readily available to serve as efficient single photon sources or quantum bits interfaced with free-space or lensed-fiber optics.