Full Manipulation Research Articles

Terahertz Beam Shaping Using Space-Time Phase-only Coded Metasurfaces

Digital metasurfaces as space-coded surfaces composed of a set of sub-wavelength meta-atoms enable extraordinary capabilities to manipulate electromagnetic waves. Recently, amplitude-phase-joint-coding metasurfaces have been proposed to achieve enhanced beam shaping. However, design of a unit cell structure with a full manipulation of amplitude and phase of the reflected beam is challenging and this kind of unit cell structures are complicated. This paper proposes a space-time phase-only metasurface based on simple graphene-based unit cell that is digitally coded and arranged with a specific time sequence, allowing the effective simultaneous manipulation of both phase and amplitude. In this way, it is demonstrated that the terahertz beam can be shaped using the proposed terahertz metasurface.

Full electrical manipulation of perpendicular exchange bias in ultrathin antiferromagnetic film with epitaxial strain

Achieving effective manipulation of perpendicular exchange bias effect remains an intricate endeavor, yet it stands a significance for the evolution of ultra-high capacity and energy-efficient magnetic memory and logic devices. A persistent impediment to its practical applications is the reliance on external magnetic fields during the current-induced switching of exchange bias in perpendicularly magnetized structures. This study elucidates the achievement of a full electrical manipulation of the perpendicular exchange bias in the multilayers with an ultrathin antiferromagnetic layer. Owing to the anisotropic epitaxial strain in the 2-nm-thick IrMn3 layer, the considerable exchange bias effect is clearly achieved at room temperature. Concomitantly, a specific global uncompensated magnetization manifests in the IrMn3 layer, facilitating the switching of the irreversible portion of the uncompensated magnetization. Consequently, the perpendicular exchange bias can be manipulated by only applying pulsed current, notably independent of the presence of any external magnetic fields.

Plant diversity and grasses increase root biomass in a rainfall and grassland diversity manipulation

The loss of plant productivity with declining diversity is well established, exceeding other global change drivers including drought. These patterns are most clearly established for aboveground productivity, it remains poorly understood whether productivity increases associated with diversity are replicated belowground. To address this gap, we established a plant diversity-manipulation experiment in 2018. It is a full factorial manipulation of plant species richness and community composition, and precipitation. Three and five years post-establishment, two bulk soil cores (20cm depth) were collected and composited from each plot and were processed for roots to determine belowground biomass as root standing crop. We observed a strong positive relationship between richness and aboveground production and belowground biomass, generating positive combined above and belowground with diversity. Root standing crop increased 1.4-fold from years three to five. Grass communities produced more root biomass (monoculture mean 463.9 ± 410.3g m−2), and the magnitude of the relationship between richness and root standing crop was greatest within those communities. Legume communities produced the fewest roots (monoculture mean 212.2 ± 155.1g m−2), and belowground standing crop was not affected by diversity. Root standing crops in year three were 1.8 times higher under low precipitation conditions, while in year five we observed comparable root standing crops between precipitation treatments. Plant family was a strong mediator of increased belowground biomass observed with diversity, with single family grass and aster families generating 1.7 times greater root standing crops in six compared to single species communities, relationships between diversity and aboveground production were consistently observed in both single-family and multiple family communities. Diverse communities with species from multiple families generated only 1.3 times the root standing crop compared to monoculture average root biomass. We surprisingly observe diverse single family communities can generate increases in root standing crops that exceed those generated by diverse multiple family communities, highlighting the importance of plant richness within plant family for a given community. These patterns have potential implications for understanding the interactions of multiple global change drivers as changes in both precipitation and plant community composition do alter whether plant production aboveground is translated belowground biomass.

Optically controlled single-valley exciton doublet states with tunable internal spin structures and spin magnetization generation

Manipulating quantum states through light-matter interactions has been actively pursued in two-dimensional materials research. Significant progress has been made toward the optical control of the valley degrees of freedom in semiconducting monolayer transition-metal dichalcogenides, based on doubly degenerate excitons from their two distinct valleys in reciprocal space. Here, we introduce a type of optically controllable doubly degenerate exciton states that come from a single valley, dubbed as single-valley exciton doublet (SVXD) states. They are unique in that their constituent holes originate from the same valence band, making possible the direct optical control of the spin structure of the excited constituent electrons. Combining ab initio GW plus Bethe-Salpeter equation (GW-BSE) calculations and a theoretical analysis method, we demonstrate such SVXD in substrate-supported monolayer bismuthene-which has been successfully grown using molecular beam epitaxy. In each of the two distinct valleys in the Brillouin zone, strong spin-orbit coupling and [Formula: see text] symmetry lead to a pair of degenerate 1s exciton states (the SVXD states) with opposite spin configurations. Any coherent linear combinations of the SVXD in a single valley can be excited by light with a specific polarization, enabling full manipulation of their internal spin configurations. In particular, a controllable net spin magnetization can be generated through light excitation. Our findings open routes to control quantum degrees of freedom, paving the way for applications in spintronics and quantum information science.

Single chip simultaneous chiral and achiral imaging based on high efficiency 3D plasmonic metalens

Abstract We propose and experimentally demonstrate a single chip metasurface for simultaneous chiral and achiral imaging and polarimetric detecting using a high efficiency three dimensional plasmonic metalens (3D-PM) with capability of designed separation of different circular polarizations. The proposed 3D-PM combines both propagating and geometric phases so that two orthogonal circular polarization components of the incidence can be precisely separated and imaged into two channels and the incident polarization state can be detected with differentiation of the two channels. One single set of an array of Au layer covered anisotropic polymethyl methacrylate elliptical nanopillars is employed, in which height of each nanopillar is added as a new design degree of freedom to realize both full phase manipulation (0–2π) and high efficiency (>0.85) with coupled equivalent Fabry–Pérot cavity and localized surface plasmons. At design wavelength of 1550 nm, experimental results show that optical resolution of both chiral and achiral images approaches the diffraction limit, extinction ratio of circular polarizations in two channels is ∼33:1, and the energy efficiency reaches ∼63 %. The proposed 3D-PM provides a new and simple way for chiral/achiral imaging and polarimetric measurement, and can be applied in integrated optics, optical communication, and biomolecule detection.

Polarization-mismatching transmissive metasurface for independent amplitude and phase control of circular polarization.

This work presents a strategy for independent control of the amplitude and phase of transmissive circular-polarization (CP) waves. The designed meta-atom consists of an elliptical-polarization receiver and a CP transmitter. By changing the axial ratio (AR) and polarization of the receiver, amplitude modulation can be realized based on polarization mismatching theory, with negligible cumbrous components. While by rotating the element, a full phase coverage enabled by the geometric phase is achieved. Subsequently, a CP transmitarray antenna (TA) with high gain and low side-lobe level (SLL) is implemented to experimentally validate our strategy, and the tested results match well with the simulated ones. During the operating band from 9.6 to 10.4 GHz, the proposed TA obtains an average SLL of -24.5 dB, a lowest SLL of -27.7 dB at 9.9 GHz, and a maximum gain of 19 dBi at 10.3 GHz, with the measured AR lower than 1 dB, which mainly benefits from high polarization purity (HPP) of the proposed elements. The proposed strategy for full amplitude-phase manipulation of CP waves together with HPP paves a way for complicated field manipulations and indicates a promising candidate in antenna applications, such as anti-jamming systems and wireless communications.

Arbitrarily rotated optical axis waveguide induced by a trimming line.

Rotated optical axis waveguides can facilitate on-chip arbitrary wave-plate operations, which are crucial tools for developing integrated universal quantum computing algorithms. In this paper, we propose a unique technique based on femtosecond laser direct writing technology to fabricate arbitrarily rotated optical axis waveguides. First, a circular isotropic main waveguide with a non-optical axis was fabricated using a beam shaping method. Thereafter, a trimming line was used to create an artificial stress field near the main waveguide to induce a rotated optical axis. Using this technique, we fabricated high-performance half- and quarter-wave plates. Subsequently, high-fidelity (97.1%) Pauli-X gate operation was demonstrated via quantum process tomography, which constitutes the basis for the full manipulation of on-chip polarization-encoded qubits. In the future, this work is expected to lead to new prospects for polarization-encoded information in photonic integrated circuits.

Spin‐Selective Full and Subtle Light Intensity Manipulation with Diatomic Metasurfaces

AbstractMetasurfaces are considered to be ideal candidates for precise and continuous manipulation of optical wave intensity at nanoscale pixels, which is the main basis of display and imaging devices. Malus's law has been widely used as the basic design principle for the realization of linearly polarized optical wave intensity manipulation. However, there is no such straightforward and concise law like Malus's law that can be used to design metasurfaces for full and subtle intensity manipulation of circularly polarized optical waves. Here, a new design strategy based on the collective interference effect in diatomic metasurfaces is presented to fill this gap, which can create a simple and complete mapping from a single structural variable to the reflection intensity of circularly polarized waves. The full and subtle intensity manipulation of circularly polarized optical waves can be conveniently realized by changing one structural parameter in the diatomic metasurface. Spin‐selective high‐level grayscale images are numerically and experimentally implemented based on the proposed diatomic metasurfaces. The proposed grayscale imaging scheme with subwavelength spatial resolution and high gray level is promising for advanced display and information encryption applications.

Programmable Wavefront Control in the Visible Spectrum Using Low-Loss Chalcogenide Phase-Change Metasurfaces.

All-dielectric metasurfaces provide unique solutions for advanced wavefront manipulation of light with complete control of amplitude and phase at sub-wavelength scales. One limitation, however, for most of these devices is the lack of any post-fabrication tunability of their response. To break this limit, a promising approach is employing phase-change materials (PCMs), which provide fast, low energy, and non-volatile means to endow metasurfaces with a switching mechanism. In this regard, great advancements have been done in the mid-infrared and near-infrared spectrum using different chalcogenides. In the visible spectral range, however, very few devices have demonstrated full phase manipulation, high efficiencies, and reversible optical modulation. In this work, a programmable all-dielectric Huygens' metasurface made of antimony sulfide (Sb2 S3 ) PCM is experimentally demonstrated, a low loss and high-index material in the visible spectral range with a large contrast (≈0.5) between its amorphous and crystalline states. ≈2π phase modulation is shown with high associated transmittance and it is used to create programmable beam-steering devices. These novel chalcogenide PCM metasurfaces have the potential to emerge as a platform for next-generation spatial light modulators and to impact application areas such as programmable and adaptive flat optics, light detection and ranging (LiDAR), and many more.

Cloth manipulation based on category classification and landmark detection

Cloth manipulation remains a challenging problem for the robotic community. Recently, there has been an increased interest in applying deep learning techniques to problems in the fashion industry. As a result, large annotated data sets for cloth category classification and landmark detection were created. In this work, we leverage these advances in deep learning to perform cloth manipulation. We propose a full cloth manipulation framework that, performs category classification and landmark detection based on an image of a garment, followed by a manipulation strategy. The process is performed iteratively to achieve a stretching task where the goal is to bring a crumbled cloth into a stretched out position. We extensively evaluate our learning pipeline and show a detailed evaluation of our framework on different types of garments in a total of 140 recorded and available experiments. Finally, we demonstrate the benefits of training a network on augmented fashion data over using a small robotic-specific data set.

Single-layer spatial analog meta-processor for imaging processing

Computational meta-optics brings a twist on the accelerating hardware with the benefits of ultrafast speed, ultra-low power consumption, and parallel information processing in versatile applications. Recent advent of metasurfaces have enabled the full manipulation of electromagnetic waves within subwavelength scales, promising the multifunctional, high-throughput, compact and flat optical processors. In this trend, metasurfaces with nonlocality or multi-layer structures are proposed to perform analog optical computations based on Green’s function or Fourier transform, intrinsically constrained by limited operations or large footprints/volume. Here, we showcase a Fourier-based metaprocessor to impart customized highly flexible transfer functions for analog computing upon our single-layer Huygens’ metasurface. Basic mathematical operations, including differentiation and cross-correlation, are performed by directly modulating complex wavefronts in spatial Fourier domain, facilitating edge detection and pattern recognition of various image processing. Our work substantiates an ultracompact and powerful kernel processor, which could find important applications for optical analog computing and image processing.

Digital Microfluidics-Powered Real-Time Monitoring of Isothermal DNA Amplification of Cancer Biomarker.

We introduce a digital microfluidics (DMF) platform specifically designed to perform a loop-mediated isothermal amplification (LAMP) of DNA and applied it to a real-time amplification to monitor a cancer biomarker, c-Myc (associated to 40% of all human tumors), using fluorescence microscopy. We demonstrate the full manipulation of the sample and reagents on the DMF platform, resulting in the successful amplification of 90 pg of the target DNA (0.5 ng/µL) in less than one hour. Furthermore, we test the efficiency of an innovative mixing strategy in DMF by employing two mixing methodologies onto the DMF droplets—low frequency AC (alternating current) actuation as well as back-and-forth droplet motion—which allows for improved fluorescence readouts. Fluorophore bleaching effects are minimized through on-chip sample partitioning by DMF processes and sequential droplet irradiation. Finally, LAMP reactions require only 2 µL volume droplets, which represents a 10-fold volume reduction in comparison to benchtop LAMP.

Persuasion with Correlation Neglect: A Full Manipulation Result

We consider an information design problem in which a sender tries to persuade a receiver that has “correlation neglect,” i.e., fails to understand that signals might be correlated. We show that a sender with unlimited number of signals can fully manipulate the receiver. Specifically, the sender can induce the receiver to hold any state-dependent posterior she wishes to. If the sender only wishes to induce a state-independent posterior, she can use fully correlated signals, but generally she needs to design more involved correlation structures. (JEL D82, D83)

Full manipulation of transparency and absorption through direct tuning of dark modes in high-Q Fano metamaterials.

Controlling the line shape of Fano resonance has continued to attract significant research attention in recent years owing to its practical applications such as lasing, biosensing, and slow-light devices. However, controllable Fano resonances always require stringent alignment of complex symmetry-breaking structures; therefore, the manipulation can only be performed with limited degrees of freedom and a narrow tuning range. This work demonstrates dark-mode excitation tuning independent of the bright mode for the first time, to the authors' knowledge, in asymmetric Fano metamaterials. Metallic subwavelength slits are arranged to form asymmetric unit cells and generate a broad and bright (radiative) Fabry-Perot mode and a sharp and dark (non-radiative) surface mode. The introduction of the independent radial and angular asymmetries realizes independent control of the Fano phase (q) and quality factor (Q). This tunability provides a dynamic phase shift while maintaining a high-quality factor, enabling switching between nearly perfect transmission and absorption, which is confirmed both numerically and experimentally. The proposed scheme for fully controlled Fano systems can aid practical applications such as phase-sensitive switching devices.

Coherent electrical control of a single electron spin in diamond nitrogen-vacancy centers

The nitrogen-vacancy (NV) color center quantum system in diamond has shown great application potential in the fields of solid-state quantum computing and quantum precision measurement because of its unique advantages such as single-spin addressing and manipulation and long quantum coherence time at room temperature. The precise manipulation technology of single spin is particularly important for the development of the application of NV center. The common spin manipulation methods used in NV center quantum system are to drive and manipulate the electron spin by resonant alternating magnetic field. In recent years, the electrical control of quantum spin has attracted extensive attention. In this paper, the use of alternating electric field to control the electron spin of NV center has been studied. The alternating electric field generated by the electrode successfully drives the Rabi oscillation of the NV center spin between the $\Delta m_s=\pm2$ magnetic-dipole forbidden energy levels of $|m_s=-1\rangle$ and $|m_s=+1\rangle$. Further studies show that the frequency of the electrically driven Rabi oscillation is controlled by the power of the driven electric field and independent of the resonant frequency of the electric field. The combination of spin electric control and magnetic control technology can realize the full manipulation of the direct transition between the three spin energy levels of NV center, thus promoting the development of the research and applications of NV quantum system in the fields of quantum simulation, quantum computing, precision measurement of electromagnetic field and so on.

Impact of a Robot Manipulation on the Dimensional Measurements in an SPC-Based Robot Cell

In our study a robot was used to deliver objects for measurement into the Equator gauging system. To investigate the robot’s manipulation influence on dimensional measurements, the robot’s tasks were divided into basic functions. Based on these basic functions, nine different robot-manipulation scenarios were defined, i.e., from zero to full robot manipulation, for two measuring objects (named Magnet and PKR) and six measurement characteristics (rectangular and spherical). The robot’s manipulation influence was determined on the basis of the statistical parameters Cp, R, and the 6σ obtained from a measurement system analysis (MSA) type-1 study. The results show that the degree of implemented manipulation of the robot affects the scattering of the measurement data. However, the effect is much more pronounced in the case of length measurements than with spherical geometries. Different measuring methods (touch-triggering or scanning measurement mode, number of sampling points) were used, which showed similar measurement data. This directly indicated the influence of the robot’s manipulation on Cp, R and 6σ. Increasing the degree of the robot’s manipulation decreases the Cp value and increases the R and 6σ values for the length measurements. There is no such pronounced course in the spherical geometries, where the values of Cp, R and 6σ remain approximately the same. The main influential factor for decreasing the Cp value with increasing robot manipulation was the angular misalignment of the object’s orientation in the fixture.

Quo Vadis, Metasurfaces?

The full manipulation of intrinsic properties of electromagnetic waves has become the central target in various modern optical technologies. Optical metasurfaces have been suggested for a complete control of light-matter interaction with subwavelength structures, and they have been explored widely in the past decade for creating next-generation multifunctional flat-optics devices. The current studies of metasurfaces have reached a mature stage where common materials, basic optical physics, and conventional engineering tools have been explored extensively for various applications such as light bending, metalenses, metaholograms, and many others. A natural question is where the future research on metasurfaces will be going: Quo vadis, metasurfaces? In this Mini Review, we provide perspectives on the future developments of optical metasurfaces. Specifically, we highlight recent progresses on hybrid metasurfaces employing low-dimensional materials and discuss biomedical, computational, and quantum applications of metasurfaces, followed by discussions of challenges and foreseeing the future of metasurface physics and engineering.

Pain Perception During the Phases of Manual Reduction of Distal End Radius Fracture With a Periosteal Block.

IntroductionClosed reduction is an effective method of treatment for distal end radius fractures. We present a case series of patients with distal end radius fractures who underwent closed manipulative reduction using the periosteal block. We describe the technique in detail and examine its efficacy in pain lowering effect during closed reduction.MethodsNineteen patients with distal end radial and ulnar fractures were included and grouped based on the Frykman classification. The reduction was performed using a periosteal block of 10 ml of 2% lignocaine injection. The severity of pain was recorded by utilizing the visual analog scale (VAS) in five phases: 1) before injection, 2) after 15 minutes of analgesia in a resting position, 3) during minimal motion, 4) during full manipulation and reduction, and 5) post-procedure. The VAS scoring was classified as painless (VAS score of 0), mild pain (VAS score between 1-3), and painful (VAS score of 4 and above).ResultsThe study included 19 patients [median age of 53 years (range: 18-88 years)]; there were 11 (58%) males and eight (42%) females. The mechanism of injury was a fall (n=12, 63%) or a motor vehicle accident (n=7, 37%). There was a statistically significant reduction of pain between phase one and all the other phases. Between the different fracture configurations, there was no significant difference in pain reduction. The most painful phase was expected to be phase four, ie, during full manipulation, in which four (21%) patients had a VAS score of 0, 12 (63%) patients had a VAS score between 1-3, and three (16%) patients had a VAS score of 4. Thus, 16 out of 19 patients (84%) had no or minimal pain during the most painful phase. There were no complications from the periosteal blocks.ConclusionsThe periosteal nerve block is an effective procedure providing satisfactory analgesia during the reduction of distal radial and ulnar fractures. It has no side effects and is free from complications associated with conventional sedation.

Recent progresses of circular polarization multiplexing engineered multi-functional metasurfaces

In this paper, the recent progresses of circular polarization (CP) multiplexing engineered multi-functional metasurfaces is reviewed. Firstly, in order to break through the physical limitation introduced by the conjugate symmetric geometric phases responses under orthogonal CP incidences, the equivalent Jones matrix of metasurface model is derived and the independent manipulation method of two cross-polarized phase responses is proposed. Furthermore, the three-channel wave-front integration method based on metasurface is proposed based on amplitude and phase relationship between co- and cross-polarized output components, which achieves the full manipulation of transmitted CP electromagnetic energy. On these basis, the concept of chirality-assisted phase and the wave-front manipulation method for all full CP channels is proposed, which enhances the utilization efficiency of CP electromagnetic energy. The results proposed in this paper can pave the solid theoretical foundation for increasing the capability of information channels and transmission rate.

Single‐Layered Reflective Metasurface Achieving Simultaneous Spin‐Selective Perfect Absorption and Efficient Wavefront Manipulation

AbstractAs the 2D counterpart of metamaterials, metasurfaces have drawn wide attentions in recent years due to their unique electromagnetic (EM) properties and subwavelength footprints. Although great efforts have been made in metasurface‐based full vectorial manipulation of EM waves, the realization of multifunctional devices with high compactness is still challenging. Here, by employing the mutual coupling between the meta‐atoms to induce spin‐selective magnetic resonance, a generalized design principle based on single‐layered metasurface is proposed that can achieve giant chiral absorption with average circular dichroism larger than 80%. In addition, arbitrary wavefront manipulation for reflected waves can also be realized with operation efficiency larger than 88%. As a proof of concept, three kinds of chiral devices including beam deflector, vortex beam generator, and meta‐hologram are numerically investigated in infrared region with high performance. It is believed that these multifunctional devices with simple geometry have great potentials in the field of chiral imaging, chiroptical spectroscopy, and EM communication.