arXiv subjects

Yuanqing Yang

Publications and source records attributed to Yuanqing Yang.

16 recordsLinked to original sources

arXiv2024

Goal-oriented Semantic Communications for Robotic Waypoint Transmission: The Value and Age of Information Approach

The ultra-reliable and low-latency communication (URLLC) service of the fifth-generation (5G) mobile communication network struggles to support safe robot operation. Nowadays, the sixth-generation (6G) mobile communication network is proposed to provide hyper-reliable and low-latency communication to enable safer control for robots. However, current 5G/ 6G research mainly focused on improving communication performance, while the robotics community mostly assumed communication to be ideal. To jointly consider communication and robotic control with a focus on the specific robotic task, we propose goal-oriented semantic communication in robotic control (GSRC) to exploit the context of data and its importance in achieving the task at both transmitter and receiver. At the transmitter, we propose a deep reinforcement learning algorithm to generate optimal control and command (C&C) data and a proactive repetition scheme (DeepPro) to increase the successful transmission probability. At the receiver, we design the value of information (VoI) and age of information (AoI) based queue ordering mechanism (VA-QOM) to rank the queue based on the semantic information extracted from AoI and VoI. The simulation results validate that our proposed GSRC framework achieves a 91.5% improvement in the mean square error compared to the traditional unmanned aerial vehicle control framework.

cs.RO↗

arXiv2024

Goal-Oriented UAV Communication Design and Optimization for Target Tracking: A MachineLearning Approach

To accomplish various tasks, safe and smooth control of unmanned aerial vehicles (UAVs) needs to be guaranteed, which cannot be met by existing ultra-reliable low latency communications (URLLC). This has attracted the attention of the communication field, where most existing work mainly focused on optimizing communication performance (i.e., delay) and ignored the performance of the task (i.e., tracking accuracy). To explore the effectiveness of communication in completing a task, in this letter, we propose a goal-oriented communication framework adopting a deep reinforcement learning (DRL) algorithm with a proactive repetition scheme (DeepP) to optimize C&C data selection and the maximum number of repetitions in a real-time target tracking task, where a base station (BS) controls a UAV to track a mobile target. The effectiveness of our proposed approach is validated by comparing it with the traditional proportional integral derivative (PID) algorithm.

eess.SY↗

arXiv2022

Preparing data for pathological artificial intelligence with clinical-grade performance

[Purpose] The pathology is decisive for disease diagnosis, but relies heavily on the experienced pathologists. Recently, pathological artificial intelligence (PAI) is thought to improve diagnostic accuracy and efficiency. However, the high performance of PAI based on deep learning in the laboratory generally cannot be reproduced in the clinic. [Methods] Because the data preparation is important for PAI, the paper has reviewed PAI-related studies in the PubMed database published from January 2017 to February 2022, and 118 studies were included. The in-depth analysis of methods for preparing data is performed, including obtaining slides of pathological tissue, cleaning, screening, and then digitizing. Expert review, image annotation, dataset division for model training and validation are also discussed. We further discuss the reasons why the high performance of PAI is not reproducible in the clinical practices and show some effective ways to improve clinical performances of PAI. [Results] The robustness of PAI depend on randomized collection of representative disease slides, including rigorous quality control and screening, correction of digital discrepancies, reasonable annotation, and the amount of data. The digital pathology is fundamental of clinical-grade PAI, and the techniques of data standardization and weakly supervised learning methods based on whole slide image (WSI) are effective ways to overcome obstacles of performance reproduction. [Conclusion] The representative data, the amount of labeling and consistency from multi-centers is the key to performance reproduction. The digital pathology for clinical diagnosis, data standardization and technique of WSI-based weakly supervised learning hopefully build clinical-grade PAI. Keywords: pathological artificial intelligence; data preparation; clinical-grade; deep learning

eess.IV↗

arXiv2021

Controllable Optical Resonances and Unidirectional Scattering by Core-shell Nanoparticles

Nanoparticles supporting a distinct series of Mie resonances have enabled a new class of nanoantennas and provide efficient ways to manipulate light at the nanoscale. The ability to flexibly tune the optical resonances and scattering directionality are particularly essential for various applications ranging from biosensing to nanolasers. In this paper, we investigate the core-shell nanoparticles that support both electric and magnetic Mie resonances and for the first time systematically reveal the mode evolution from a pure high-index dielectric nanosphere to a pure plasmonic one, where it has a sudden transition when core-shell ratio increases from 0.4 to 0.5. Furthermore, by engineering the electric and magnetic resonances, we demonstrate the unidirectional forward and backward scattering in such a system and reveal its tunability via geometric tuning.

physics.optics↗

arXiv2020

Engineering nanoparticles with pure high-order multipole scattering

The ability to control scattering directionality of nanoparticles is in high demand for many nanophotonic applications. One of the challenges is to design nanoparticles producing pure high-order multipole scattering (e.g., octopole, hexadecapole), whose contribution is usually negligible compared to strong low-order multipole scattering (i.e., dipole or quadrupole). Here we present an intuitive way to design such nanoparticles by introducing a void inside them. We show that both shell and ring nanostructures allow regimes with nearly pure high-order multipole scattering. Experimentally measured scattering diagrams from properly designed silicon rings at near-infrared wavelengths (~ 800 nm) reproduce well scattering patterns of an electric octopole and magnetic hexadecapole. Our findings advance significantly inverse engineering of nanoparticles from given complex scattering characteristics, with possible applications in biosensing, optical metasurfaces, and quantum communications.

physics.optics↗

arXiv2019

Multifunctional Metamirrors Involving Simultaneous Linear-polarization Conversion and Focusing

Reducing a set of diverse bulk-optic-based optical components to a single ultrathin and compact element that enables the same complex functionality has become an emerging research area, propelling further integration and miniaturization in photonics. In this work, we establish a versatile metasurface platform based on gap-surface plasmon meta-atoms enabling efficient linear-polarization conversion along with the complete phase control over reflected fields. Capitalizing on the meta-atom design, multifunctional metamirrors involving linear-polarization conversion and focusing are experimentally demonstrated to generate various kinds of focused beams with distinct phase distributions and wavefronts, reproducing thereby the combined functionalities of conventional half-wave plates, lenses, and even spatial light modulators. The proof-of-concept fabricated metamirrors exhibit excellent capability of linear-polarization conversion and focusing within the wavelength range from 800 to 950 nm under linearly-polarized excitation. The multifunctional metamirrors design developed in this study opens new avenues in the advanced research and applications targeting photonics integration of diversified functionalities.

physics.optics↗

arXiv2019

Unidirectional single-photon emission from germanium-vacancy zero-phonon lines: Deterministic emitter-waveguide interfacing at plasmonic hot spots

Striving for nanometer-sized solid-state single-photon sources, we investigate atom-like quantum emitters based on single germanium vacancy (GeV) centers isolated in crystalline nanodiamonds (NDs). Cryogenic characterization indicated symmetry-protected and bright (> 10^6 counts/s with off-resonance excitation) zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e., up to 870 GHz in highly strained NDs vs 150 GHz in bulk). Utilizing lithographic alignment techniques, we demonstrate an integrated nanophotonic platform for deterministic interfacing plasmonic waveguides with isolated GeV centers in NDs that enables 10-fold enhancement of single-photon decay rates along with the emission direction control by judiciously designing and positioning a Bragg reflector. This approach allows one to realize the unidirectional emission from single-photon dipolar sources introducing a novel method that is alternative to the propagation-direction-dependent techniques based on chiral interactions or topological protection. The developed plasmon-based nanophotonic platform opens thereby new perspectives for quantum nanophotonics in general and for realizing entanglement between single photons and spin qubits, in particular.

physics.app-ph↗

arXiv2018

On-chip detection of spin-selective routing in plasmonic nanocircuits

On-chip manipulating and controlling the temporal and spatial evolution of light is of crucial importance for information processing in future planar integrated nanophotonics. The spin and orbital angular momentum of light, which can be treated independently in classical macroscopic geometrical optics, appear to be coupled on subwavelength scales. We use spin-orbit interactions in a plasmonic achiral nano-coupler to unidirectionally excite surface plasmon polariton modes propagating in seamlessly integrated plasmonic slot waveguides. The spin-dependent flow of light in the proposed nanophotonic circuit allows on-chip electrical detection of the spin state of incident photons by integrating two germanium-based plasmonic-waveguide photodetectors. Consequently, our device serves as a compact ($\sim$ 6 $\times$ 18 $μ$m$^2$) electrical sensor for photonic spin Hall dynamics. The demonstrated configuration opens new avenues for developing highly-integrated polarization-controlled optical devices that would exploit the spin-degree of freedom for manipulating and controlling subwavelength optical modes in nanophotonic systems.

physics.optics↗

arXiv2018

Nonradiating anapole states in nanophotonics: from fundamentals to applications

Nonradiating sources are nontrivial charge-current distributions that do not generate fields outside the source domain. The pursuit of their possible existence has fascinated several generations of physicists and triggered developments in various branches of science ranging from medical imaging to dark matter. Recently, one of the most fundamental types of nonradiating sources, named anapole states, has been realized in nanophotonics regime and soon spurred considerable research efforts and widespread interest. A series of astounding advances have been achieved within a very short period of time, uncovering the great potential of anapole states in many aspects such as lasing, sensing, metamaterials, and nonlinear optics. In this review, we provide a detailed account of anapole states in nanophotonics research, encompassing their basic concepts, historical origins, and new physical effects. We discuss the recent research frontiers in understanding and employing optical anapoles and provide an outlook for this vibrant field of research.

physics.optics↗

arXiv2018

Ultra-compact branchless plasmonic interferometers

Miniaturization of functional optical devices and circuits is a key prerequisite for a myriad of applications ranging from biosensing to quantum information processing. This development has considerably been spurred by rapid developments within plasmonics exploiting its unprecedented ability to squeeze light into subwavelength scale. In this study, we investigate on-chip plasmonic systems allowing for synchronous excitation of multiple inputs and examine the interference between two adjacent excited channels. We present a branchless interferometer consisting of two parallel plasmonic waveguides that can be either selectively or coherently excited via ultra-compact antenna couplers. The total coupling efficiency is quantitatively characterized in a systematic manner and shown to exceed 15% for small waveguide separations, with the power distribution between the two waveguides being efficiently and dynamically shaped by adjusting the incident beam position. The presented design principle can readily be extended to other configurations, giving new perspectives for highly dense integrated plasmonic circuitry, optoelectronic devices, and sensing applications.

physics.app-ph↗

arXiv2018

Interference in edge-scattering from monocrystalline gold flakes

We observe strongly dissimilar scattering from two types of edges in hexagonal quasi-monocrystalline gold flakes with thicknesses around 1 micron. We identify as the origin the interference between a direct, quasi-specular scattering and an indirect scattering process involving an intermediate surface-plasmon state. The dissimilarity between the two types of edges is a direct consequence of the three-fold symmetry around the [111]-axis and the intrinsic chirality of a face-centered cubic lattice. We propose that this effect can be used to estimate flake thickness, crystal morphology, and surface contamination.

physics.optics↗

arXiv2018

Laser writing of bright colours on near-percolation plasmonic reflector arrays

Colouration by surface nanostructuring has attracted a great deal of attention by the virtue of making use of environment-friendly recyclable materials and generating non-bleaching colours [1-8]. Recently, it was found possible to delegate the task of colour printing to laser post-processing that modifies carefully designed and fabricated nanostructures [9,10]. Here we take the next crucial step in the development of structural colour printing by dispensing with preformed nanostructures and using instead near-percolation metal films atop dielectric-metal sandwiches, i.e., near-percolation plasmonic reflector arrays. Scanning rapidly (~ 20 μm/s) across 4-nm-thin island-like gold films supported by 30-nm-thin silica layers atop 100-nm-thick gold layers with a strongly focused Ti-sapphire laser beam, while adjusting the average laser power from 1 to 10 mW, we produce bright colours varying from green to red by laser-heating-induced merging and reshaping of gold islands. Selection of strongly heated islands and their reshaping, both originating from the excitation of plasmonic resonances, are strongly influenced by the polarization direction of laser illumination, so that the colours produced are well pronounced only when viewed with the same polarization. Conversely, the laser colour writing with circular polarizations results in bright polarization-independent colour images. The fabrication procedure for near-percolation reflector arrays is exceedingly simple and scalable to mass production, while the laser-induced modification occurs inherently with the subwavelength resolution. This unique combination of remarkable features makes the approach developed for laser colour writing readily amenable for practical implementation and use in diverse applications ranging from nanoscale patterning for security marking to large-scale colour printing for decoration.

physics.app-ph↗

arXiv2018

Dynamic control of anapole states with phase-change alloys

High-index dielectric nanoparticles supporting a distinct series of Mie resonances have enabled a new class of optical antennas with unprecedented functionalities. The great wealth of multipolar responses and their delicate interplay have not only spurred practical developments but also brought new insight into fundamental physics such as the recent observation of nonradiating anapole states in the optical regime. However, how to make such a colorful resonance palette actively tunable and even switchable among different elemental multipoles is still elusive. Here, for the first time, we demonstrate both theoretically and experimentally that a structured phase-change alloy Ge$_2$Sb$_2$Te$_5$ (GST) can support a diverse set of multipolar Mie resonances with active tunability and switchability. By harnessing the dramatic optical contrast (Δn > 2) and the intermediate phases of the GST material, we realize continuous switching between a scattering bright state (electric dipole mode) and a dark state (anapole mode) in a broadband range (Δλ > 600 nm). Dynamic control of higher-order anapoles and resulting multimodal switching effects are also systematically investigated, which naturally make the structured GST serve as a multispectral optical switch with high extinction contrasts (> 6 dB) and multi-level control capabilities. With all these findings, our study provides an entirely new design principle for realizing active nanophotonic devices.

physics.optics↗

arXiv2018

Anapole-Assisted Strong Field Enhancement in Individual All-Dielectric Nanostructures

High-index dielectric nanostructures have recently become prominent forefront alternatives for manipulating light at the nanoscale. Their electric and magnetic resonances with intriguing characteristics endow them with a unique ability to strongly enhance near-field effects with minimal absorption. Similar to their metallic counterparts, dielectric oligomers consisting of two or more coupled particles are generally employed to create localized optical fields. Here we show that individual all-dielectric nanostructures, with rational designs, can produce strong electric fields with intensity enhancements exceeding 3 orders of magnitude. Such a striking effect is demonstrated within a Si nanodisk by fully exploiting anapole generation and simultaneously introducing a slot area with high-contrast interfaces. By performing finite-difference time-domain simulations and multipole decomposition analysis, we systematically investigate both far-field and near-field properties of the slotted disk and reveal a subtle interplay among different resonant modes of the system. Furthermore, while electric fields at anapole modes are typically internal, i.e., found inside nanostructures, our slotted configuration generates external hotspots with electric fields additionally enhanced by virtue of boundary conditions. These electric hotspots are thereby directly accessible to nearby molecules or quantum emitters, opening up new possibilities for single-particle enhanced spectroscopies or single-photon emission enhancement due to large Purcell effects. Our presented design methodology is also readily extendable to other materials and other geometries, which may unlock enormous potential for sensing and quantum nanophotonic applications.

physics.optics↗

arXiv2017

Direct amplitude-phase near-field observation of higher-order anapole states

Anapole states associated with the resonant suppression of electric-dipole scattering exhibit minimized extinction and maximized storage of electromagnetic energy inside a particle. Using numerical simulations, optical extinction spectroscopy and amplitude-phase near-field mapping of silicon dielectric disks, we demonstrate high-order anapole states in the near-infrared wavelength range (900-1700 nm). We develop the procedure for unambiguously identifying anapole states by monitoring the normal component of the electric near-field and experimentally detect the first two anapole states as verified by far-field extinction spectroscopy and confirmed with the numerical simulations. We demonstrate that higher order anapole states possess stronger energy concentration and narrower resonances, a remarkable feature that is advantageous for their applications in metasurfaces and nanophotonics components, such as non-linear higher-harmonic generators and nanoscale lasers.

physics.optics↗

arXiv2017

Multimode directionality in all-dielectric metasurfaces

We demonstrate that spectrally diverse multiple magnetic dipole resonances can be excited in all-dielectric structures lacking rotational symmetry, in contrast to conventionally used spheres, disks or spheroids. Such multiple magnetic resonances arise from hybrid Mie-Fabry-Pérot modes, and can constructively interfere with induced electric dipole moments, thereby leading to novel multi-frequency unidirectional scattering. Here we focus on elongated dielectric nanobars, whose magnetic resonances can be spectrally tuned by their aspect ratios. Based on our theoretical results, we suggest all-dielectric multimode metasurfaces and verify them in proof-of-principle microwave experiments. We also believe that the demonstrated property of multimode directionality is largely responsible for the best efficiency of all-dielectric metasurfaces that were recently shown to operate across multiple telecom bands.

physics.optics↗