Field Illumination Research Articles

Highly localized continuous wave optical vortex with controllable orbital angular momentum orientation and topological charge.

We report an approach to simultaneously control orbital angular momentum (OAM) orientation and topological charge in highly localized optical vortices by employing a 4π focusing system. The required continuous wave illumination field in the pupil planes is derived by superimposing the radiation pattern of only one dipole placed at the focal point of the high numerical aperture lens and the corresponding tailored spiral phase factor. The topological charge and OAM orientation of the obtained focused fields are quantitatively evaluated based on the focal field distributions calculated by the Richards-Wolf vector diffraction integration theory. Results show that the OAM of the generated optical vortices can be tailored by changing the oscillation orientation of the mimic dipole and the topological charge of the superimposed spiral phase term. The presented method may find potential applications in optical trapping, optical tweezers, light-matter interaction, etc.

Fast object imaging and classification based on circular harmonic Fourier moment detection.

Limited by the number of illumination fields and the speed of a spatial light modulator, single-pixel imaging (SPI) cannot realize real-time imaging and fast classification of an object. In this paper, we proposed the circular harmonic Fourier single-pixel imaging (CHF-SPI) for the first time to realize fast imaging and classification of objects. The light field distribution satisfies the circular harmonic Fourier formula, and the light intensity values of the single-pixel detector are equivalent to the circular harmonic Fourier moments. Then the target can be reconstructed under low sampling ratio by inverse transformation. Through simulation and experimental verification, clear imaging can be performed at a sampling ratio of 0.9%. In addition, circular harmonic Fourier moments are used to construct multi-distortion invariant to classify objects with rotation and scale change. The scale change multiples of objects can be calculated and the objects can be classified by using 10 light fields. It is of great significance to classify objects quickly without imaging.

Near-Field Matching and Universal Limits on Electromagnetic Energy Transfer

This article introduces the concept of near-field (NF) matching as a continuum-mode generalization of port matching in circuit theory suitable for field-theoretic electromagnetic energy transfer scenarios, with a focus on spatio-frequency processes in coupled systems. The concept is rigorously formulated using the full electromagnetic Green’s function of a generic receiving surface interacting with arbitrary illumination fields where the Riemannian structure and the electromagnetic boundary condition of the problem are encoded into the tensor structure of a Green’s function on a manifold. After a carefully selected combination of proper function spaces for the various field quantities involved, we utilize exact methods to estimate the sizes of various operator quantities using the appropriate function space norms. A field-theoretic measure of power transfer efficiency in generalized NF matching scenarios is introduced, and exact upper bounds on this efficiency are derived using Young’s inequality for integral kernel operators. This theoretical study complements and generalizes the largely empirical and problem-specific literature on wireless energy transfer by providing an exact and rigorous mathematical framework that can guide and inform future optimization and design processes.

Single image relighting based on illumination field reconstruction.

Relighting a single low-light image is a crucial and challenging task. Previous works primarily focused on brightness enhancement but neglected the differences in light and shadow variations, which leads to unsatisfactory results. Herein, an illumination field reconstruction (IFR) algorithm is proposed to address this issue by leveraging physical mechanism guidance, physical-based supervision, and data-based modeling. Firstly, we derived the Illumination field modulation equation as a physical prior to guide the network design. Next, we constructed a physical-based dataset consisting of image sequences with diverse illumination levels as supervision. Finally, we proposed the IFR neural network (IFRNet) to model the relighting progress and reconstruct photorealistic images. Extensive experiments demonstrate the effectiveness of our method on both simulated and real-world datasets, showing its generalization ability in real-world scenarios, even training solely from simulation.

Hybrid graphene - silver nanoantenna to control THz emission from polar quantum systems.

Fluorescent light emission from atomic quantum systems routinely occurs at the illumination frequency. If the system is polar, an additional fluorescence peak appears at a much lower Rabi frequency, which scales with the illumination field amplitude. This opens the possibility of spectrally controlling the emission, promising tunable coherent radiation sources. However, typically the emission occurs in the MHz to GHz regimes, and its intensity from a single quantum system is relatively low. Here, we propose a hybrid nanoantenna combining noble-metal and graphene elements, exploited for an unusual goal: The silver elements spectrally tune the emission frequency of the molecule and shift it to the THz band, where novel sources of coherent radiation are still desired. Additionally, the graphene elements are used to plasmonically enhance the emission intensity. Their tunability allows for adjustment of the operational frequencies of the device to the illumination conditions and to counteract the fluctuations related to the field modulations in space. All these features are discussed based on the real-life example of a polar molecule of barium monofluoride (BaF).

Super-resolution imaging system developed from vector superoscillatory field illumination.

Superoscillations are oscillations of a band limited waveform with a local frequency higher than the bandlimit. Spatial superoscillations show great potential for performing super-resolution imaging. However, these superoscillatory waveforms are inevitably surrounded by high intensity sidelobes which severely limit the usable super-resolved area of an image. In this study, we demonstrate how polarization engineering can be used in some circumstances to suppress superoscillation sidelobes, taking advantage of the transverse wave nature of light. We illustrate the principle by a model super-resolution imaging system that can image Rayleigh scatterers with separations smaller than the classic Rayleigh criterion.

Optical High-Speed Rolling Mark Detection Using Object Detection and Levenshtein Distance

This paper presents an automated high-speed rolling mark recognition system for railroad rails utilizing image processing techniques. Rolling marks, which consist of numbers, letters, and special characters, were engraved into the rail web as 3D information. These rolling marks provide crucial details regarding the rail manufacturer, steel quality, year of production, and rail profile. As a result, they empower rail infrastructure managers to gain valuable insights into their infrastructure. The rolling marks were captured using a standard color camera under dark field illumination. The recognition of individual numbers, letters, and special characters was achieved through state-of-the-art deep neural network object detection, specifically employing the YOLO architecture. By leveraging reference rolling marks, the detected characters can then be accurately interpreted and corrected. This correction process involves calculating a weighted Levenshtein distance, ensuring that the system can identify and rectify partially misidentified rolling marks. Through the proposed system, the accurate and reliable identification of rolling marks was achieved, even in cases in which there were partial errors in the detection process. This novel system thus has the potential to substantially improve the management and maintenance of railroad infrastructure.

Developing a new persistent luminescence material by introducing cation defects

Crystal defects significantly impact luminescent properties, particularly for thermal stability and persistent luminescence (PersL). In this study, a new Ce3+ doped phosphor K3GdSi2O7:xCe3+ is synthesized at a high temperature of 1200 °C with interesting PersL. Based on electron paramagnetic resonance spectra, there is a cation defect in the K3GdSi2O7:xCe3+ phosphor. We deduce that the principal source of defect is K+ vacancy mainly because of the aliovalent substitution of K+ by Ce3+. The K+ forms a number of trap energy levels, which can be confirmed by a thermoluminescence study. Within the range of 10–225 K, the intensity of the emission increases with the increase in temperature, due to the energy release of deep-level traps. At room temperature, K3GdSi2O7:0.05Ce3+ shows PersL of about 728 s induced by shallow-level traps. We think that K3GdSi2O7:0.05Ce3+ is a potential PersL material for applications in fields of emergency illumination, traffic indication, anti-counterfeiting, and information security.

Mixed-Halide Perovskites with Halogen Bond Induced Interlayer Locking Structure for Stable Pure-Red PeLEDs.

Mixed-halide perovskites enable precise spectral tuning across the entire spectral range through composition engineering. However, mixed halide perovskites are susceptible to ion migration under continuous illumination or electric field, which significantly impedes the actual application of perovskite light-emitting diodes (PeLEDs). Here, we demonstrate a novel approach to introduce strong and homogeneous halogen bonds within the quasi-two-dimensional perovskite lattices by means of an interlayer locking structure, which effectively suppresses ion migration by increasing the corresponding activation energy. Various characterizations confirmed that intralattice halogen bonds enhance the stability of quasi-2D mixed-halide perovskite films. Here, we report that the PeLEDs exhibit an impressive 18.3% EQE with pure red emission with CIE color coordinate of (0.67, 0.33) matching Rec. 2100 standards and demonstrate an operational half-life of ∼540 min at an initial luminance of 100 cd m-2, representing one of the most stable mixed-halide pure red PeLEDs reported to date.

Triple-Mode Resonant Backfire Feed Antenna With Nearly Equal E-/H-Plane and Inverse Taper Patterns

A design approach to triple-mode resonant feed antenna is advanced for parabolic reflector antenna system. The antenna is composed of a slit-loaded 1.5-wavelength sectorial dipole, a primary corner reflector, and an auxiliary circular reflector. The corner angle of the primary reflector can be employed to properly narrow down the H-plane half-power beam width (HPBW), while with the E-plane one rarely affected, such that equal E-/H-plane characteristic can be yielded accordingly. Unlike traditional backfire antennas, high-order resonant modes are employed to generate inverse taper radiation pattern at the high frequency band. As is numerically demonstrated and experimentally validated, the corner angle of the primary reflector can be eventually determined as 45∘. The antenna exhibits an impedance bandwidth of up to about 79.7%, and a nearly equal E-/H-plane bandwidth of up to about 29.4%. Average HPBW of about 65∘, gain up to about 8.9 dBi with fluctuation of less than 1 dB can be achieved within the equal E-/H-plane bandwidth. The inverse taper radiation pattern at the high frequency band can provide effective edge illumination and uniform aperture field distribution in parabolic reflector antenna systems.

Unstable wave patterns of information in neural network under light illumination and magnetic field

Functional neurons built from neural circuits are capable of perceiving and processing external signals such as light illumination and magnetic radiation, by converting the physical signals into modulated bioelectric signals called action potential with diverse forms and shapes. Through modulational instability (MI), modulated wave formation and pattern transition are studied in a chain memristive network of [Formula: see text] photosensitive neurons. Memristors and photocells are incorporated in a simple FitzHugh–Nagumo neuron to detect and process the external magnetic flux and light illumination. To determine regions of modulated wave formation, linear stability analysis is performed on a nonlinear envelope equation which resulted from the asymptotic expansion of the generic dynamical equations. The growth rate of MI is plotted and the distinct zones of stable/unstable MI are presented. We confirm the analytical result through numerical simulations whereby the initial plane wave solutions lead to the emergence of localized structures with traits of spiking, bursting and chaotic states. High-frequency photocurrent changes orderly localized patterns to chaotic-like patterns while high-frequency magnetic flux promotes pattern transition from bursting to 2-period spiking state and a 4-period spiking state. This could provide an adequate way to influence the behaviors of artificial neurons as well as potential mechanism of information coding in the nervous system.

Synthesis of Eu3+-Doped NaGd9Si6O26 Sub-Microcrystals from a NaGdF4@SiO2 Structure.

Rare earth silicate phosphors of high quantum efficiency with a stable performance are promising materials in the fields of display and illumination. The grain sizes of products synthesized via the conventional solid-state reaction method are usually too large to satisfy the requirements of color cast and extraction efficiency in high-resolution light-emitting devices (LEDs). We designed a synthetic route and successfully fabricated rare earth silicate NaGd9Si6O26 (NGSO) sub-microcrystals with a size ranging from 550 to 1200 nm. The reaction mechanism and optical properties were systematically investigated. The quantum efficiency of Eu3+-activated NGSO sub-microcrystals was about 36.6%. The LED encapsulated with these sub-microcrystals showed lower color deviation and higher lumen efficiency and lumen flux compared to that with NGSO fabricated using the conventional solid state reaction method.

Chiral Smith–Purcell Radiation Light Source

AbstractSmith–Purcell radiation (SPR) with broadly tunable spectra has attracted attention in light emission, and this free‐electron‐driven source shows great potential in illumination fields, such as terahertz sources, ultra‐compact light sources, free‐electron lasers, etc. However, it remains difficult to control the polarization properties of SPR and realize a free‐electron chiral light source. In this work, the chiral SPR with the maximum chirality (>40%) is acquired in a periodic stacked nanosquare light‐well, and the radiation chirality is manipulated by variations of the designed electron beam excitation positions. Furthermore, this work reveals that the chiroptical effect originates in the superposition of SPRs with different phases and polarization, which are derived from adjacent sidewalls. This work may deepen the comprehension of electron‐matter interaction and facilitate the development of compact electron‐driven chirality‐tunable source‐on‐chip, highlighting potential applications in photonic integration and binary data processing.

Three-dimensional localization microscopy with increased axial precision through TIRF angle modulation

To better understand the interactions between biological molecules, a high optical resolution in all three dimensions is crucial. The intrinsically lower axial resolution of microscopes however, is a limiting factor in fluorescence imaging, correspondingly in fluorescence based single molecule localization microscopy (SMLM). Here, we present a method to improve the axial localization precision in SMLM by combining point-spread-function engineering with total internal reflection fluorescence (TIRF) fields with decay lengths that vary within the on-time of a fluorophore. Such time-varying illumination field intensity allows one to extract additional axial location information from the emitted photons. With this time varying illumination approach, we show that axial localization is improved two-fold over TIRF-based SMLM using astigmatic PSFs. We calculate theoretical resolution gains for various imaging conditions via the Cramér Rao Lower Bound (CRLB), a commonly used metric to compute the best attainable localization precision in SMLM.

Ce:LYSO, from scintillator to solid-state lighting as a blue luminescent concentrator

Cerium-doped lutetium-yttrium oxyorthosilicate (Ce:LYSO) is a well-known single crystal scintillator used in medical imaging and security scanners. Recent development of high power UV LED, matching its absorption band, questions the possibility to use Ce:LYSO in a new way: as LED-pumped solid-state light source. Since Ce:LYSO is available in large size crystals, we investigate its potential as a luminescent concentrator. This paper reports an extensive study of the performance in close relation to the spectroscopic properties of this crystal. It gives the reasons why the Ce:LYSO crystal tested in this study is less efficient than Ce:YAG for luminescent concentration: limited quantum efficiency and high losses coming from self-absorption and from excited-state absorption are playing key roles. However, we demonstrate that a Ce:LYSO luminescent concentrator is an innovative source for solid-state lighting. Pumped by a peak power of 3400 W in quasi-continuous wave regime (40 µs, 10 Hz), a rectangular (1 × 22 × 105 mm3) Ce:LYSO crystal delivers a broadband spectrum (60 nm FWHM) centered at 430 nm. At full output aperture (20 × 1 mm2), it emits a peak power of 116 W. On a squared output surface (1 × 1 mm2) it emits 16 W corresponding to a brightness of 509 W cm–2 sr–1. This combination of spectrum power and brightness is higher than blue LEDs and opens perspectives for Ce:LYSO in the field of illumination namely for imaging.

Peptide-Based Fibrin-Targeting Fluorescent Probes for Murine Stasis Venous Thrombus Resolution

Background- The lack of a stasis venous thrombosis model (VT) in female mice has limited investigation of sex differences of anti-VT therapies, such as acetylsalicylic acid (ASA), which appears efficacious in preventing recurrent VT. Here we (i) develop a new extended stasis VT model; and (ii) examine the effects of ASA on stasis VT resolution in both female and male mice using serial intravital microscopy (IVM). Method- To extend stasis thrombus persistence beyond a single ligation (SL) model, the femoral vein was ligated, followed by a second ligation of saphenous vein near popliteal vein (Fig. A). Following FITC-dextran injection (10 mg/kg), FITC light irradiation (475/35nm, 20x) for three minutes across three illumination fields generated stasis VT. Subsequently, Dylight-649-GPIbβ agent was injected (100ug/kg, ex 630nm) to observe platelets. At T30’, fibrin targeting agent-FTP11-CyAm7 (150nmol/kg, ex 750 nm) was injected. ASA pre-treatment was done for 7 days (3mg/kg, n=5-6). Serial epifluorescence IVM images were acquired up to 24 hours (90i, NIS Elements software, Nikon). Thrombus area was quantified (NIH ImageJ). Results- DL thrombus was significantly larger and visualized through 24 hours (Fig B-G) and 48 hours (data not shown) versus SL thrombus (Fig. E). Corresponding sections of thrombus at T60’, T6h and T24h showed formation of a persistent thrombus core consisting platelets and fibrin (Fig. H-J). In the DL model, females developed reproducible stasis VT burden and resolution profiles as in males (Fig. K). ASA pre-treatment resulted in significant reduction in thrombus induction (T0’), and accelerated resolution in both sexes (Fig. L-P). ASA inhibited platelet recruitment to thrombi within T30’, consistent with its known anti-platelet effect via irreversible inhibition of Thromboxane A2. Furthermore, ASA inhibited fibrinogenesis, suggestive of an impaired platelet-fibrin interface. Conclusion- Here we establish a new extended stasis VT model applicable to both female and male mice that develops thrombus for up to 48 hours. Moreover, this model is amenable to study vein wall fibrosis-key aspect of post-thrombotic syndrome. Furthermore, ASA inhibits thrombus formation and accelerates thrombus resolution in a sex-independent manner, supporting its use in prevention of recurrent VT. AHA 953662; NIH 1R21AR081535-01; NIH R01GM126062 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Stimuli-Induced Subconformation Transformation of the PSI-LHCI Protein at Single-Molecule Resolution.

Photosynthesis is a very important process for the current biosphere which can maintain such a subtle and stable circulatory ecosystem on earth through the transformation of energy and substance. Even though been widely studied in various aspects, the physiological activities, such as intrinsic structural vibration and self-regulation process to stress of photosynthetic proteins, are still not in-depth resolved in real-time. Herein, utilizing silicon nanowire biosensors with ultrasensitive temporal and spatial resolution, real-time responses of a single photosystem I-light harvesting complex I (PSI-LHCI) supercomplex of Pisum sativum to various conditions, including gradient variations in temperature, illumination, and electric field, are recorded. Under different temperatures, there is a bi-state switch process associated with the intrinsic thermal vibration behavior. When the variations of illumination and the bias voltage are applied, two additional shoulder states, probably derived from the self-conformational adjustment, are observed. Based on real-time monitoring of the dynamic processes of the PSI-LHCI supercomplex under various conditions, it is successively testified to promising nanotechnology for protein profiling and biological functional integration in photosynthesis studies.

Compact ultraviolet light-emitting diode-based lithography illumination system with tunable coherent factor

Optimization of the illumination system of an ultraviolet light-emitting diode (UVLED)-based lithography system by reducing the system complexity and spatial volume has been a research focus. This work proposes a compact lithography illumination system that applies a specially designed embedded compound parabolic concentrator (ECPC) to replace the traditional collimation module and the zoom lenses module. The ECPC, comprised of two detachable parabolic surfaces, precisely collimates all light beams from the UVLED to a preset divergence angle of 6 deg and provides an adjustable lithography coherent factor. The final illumination system offers a square illumination field with a uniformity of up to 1.3% in the large coherent factor and a linearly adjustable numerical aperture in the range of 0.02 ∼ 0.04. The final exposure result of 0.7 μm based on the experiment setup further verifies the performance of the designed illumination system.

Synthesis of Pb‐free Double‐Perovskite Heterojunction (Cs2SnCl6‐Bi3+&Te4+/Cs2GeF6‐Mn4+) with White Emission for LED Application

AbstractLead‐free halide double perovskites have been extensively studied for their application in the display and lighting fields. Owing to their characteristic single white luminescence, double perovskites have led to several developments in the field of white light illumination. However, most of these materials possess poor ambient stability or produce white emissions with high correlated color temperature (CCT) and low color rendering index (Ra), which hinder their application to home and commercial lighting displays. To address these challenges, a Pb‐free double perovskite heterojunction phosphor for white light is designed, namely Cs2SnCl6‐2%Bi3+&4%Te4+/Cs2GeF6‐0.11%Mn4+, which has a low CCT of 3525 K, a high Ra of 90.5, good optical moisture and thermal stability. The pattern and mechanism of epitaxial growth are derived from structural and surface tests. Analyzing the optical properties clarifies the existence of energy transfer modes in this heterojunction material, i.e., from Bi3+ to Te4+, from Bi3+ to Mn4+, and from Te4+ to Mn4+. These results indicate the application prospects of these heterojunction phosphors in the field of white light illumination.

Detecting two-spotted spider mites and predatory mites in strawberry using deep learning

Strawberries are an important and high-value crop in the United States. The total value of strawberry production in the United States was $3.42 billion in 2021. However, a major pest of strawberries, two-spotted spider mites (TSSM) (Tetranychus urticae Koch), can cause severe economic losses due to mites feeding on chlorophyll which interferes with photosynthesis. Predatory mites (Neoseiulus californicus and Phytoseiulus persimilis) can control TSSM populations and provide an alternative to conventional pesticides. Predatory mites are more friendly to the environment than pesticides. To monitor TSSM and predatory mite populations in the field, frequent sampling is required. However, manual counting of mites using a hand lens is challenging for a large field. Therefore, this study applied deep learning models to detect TSSM and predatory mites in strawberries from smartphone images. Three different smartphones (Motorola Moto E5 Play, OnePlus A5000, and iPhone XR) and a 25x macro lens were used to collect a total of 3,013 images, including 1,779 TSSM images and 1,234 predatory mite images. TSSM images were collected by the three smartphones, and only the OnePlus A5000 and iPhone XR were used to collect predatory mite images that only contained predatory mites or contained both predatory mites and TSSM in the same image. TSSM images were used to compare two deep learning models (YOLOv4 and Faster R-CNN Resnet50) and three different smartphone cameras. This study found that the average detection accuracy of YOLOv4 and Faster R-CNN was 0.935 and 0.863, respectively. Deep learning models achieved the best detection accuracy on the image collected by iPhone XR. The YOLOv4 model was trained to compare the detection performance of three different input image sizes (160 × 160, 320 × 320, 640 × 640 pixels) for TSSM and predatory mite detection. This study found that the mean average precision of the YOLOv4 increased as the image size increased, and the model trained with an image size of 640 × 640 pixels achieved the detection accuracy of 0.933 for TSSM and predatory mites. This study also found that the YOLOv4 could detect pests under different field illumination conditions. The smartphone image-based method can detect the TSSM and predatory mites quickly from images and with high detection accuracy, which can help growers use less time to monitor mite populations in the field.