Versatile Control Research Articles

Metasurfaces on silicon photonic waveguides for simultaneous emission phase and amplitude control.

Chip-scale photonic systems that manipulate free-space emission have recently attracted attention for applications such as free-space optical communications and solid-state LiDAR. Silicon photonics, as a leading platform for chip-scale integration, needs to offer more versatile control of free-space emission. Here we integrate metasurfaces on silicon photonic waveguides to generate free-space emission with controlled phase and amplitude profiles. We demonstrate experimentally structured beams, including a focused Gaussian beam and a Hermite-Gaussian TEM10 beam, as well as holographic image projections. Our approach is monolithic and CMOS-compatible. The simultaneous phase and amplitude control enable more faithful generation of structured beams and speckle-reduced projection of holographic images.

Quantum sensing tools to characterize physical, chemical and biological processes with magnetic resonance

Nuclear Magnetic Resonance (NMR) plays a central role in developing quantum information sciences and technologies. Key features such as its non-invasive nature and the ability to process information on nuclear spins by versatile quantum control designs with electromagnetic fields, have made NMR to become a powerful technique for sensing systems from atomic and molecular scales with spectroscopy to millimeters in imaging. This brief overview provides quantum sensing tools with which we are contributing from Latin America, by combining quantum dynamical control and estimation strategies with NMR methods to probe physical, chemical, and biological processes. It introduces the basic and key concepts on how controlled spin-sensors can monitor the correlation dynamics of their environment, and selectively and optimally infer its relevant parameters. Then these concepts are illustrated with state-of-the-art implementations for characterizing (i) biological tissue microstructure with diffusion weighting imaging, (ii) quantum information dynamics and scrambling in out-of-equilibrium systems with solid-state NMR quantum simulations, and (iii) molecular structures by selective estimation of spin–spin couplings and online learning control designs with experimental proposals. We expect these concepts will motivate the development of quantum dynamical control of spin sensors to monitor systems in a variety of fields, and in particular to exploit the non-invasive strength of NMR, e.g. in biomedical diagnosis.

Multiple phase transitions and anomalous non-Hermitian skin effect

Non-Hermiticity is revolutionizing the common understanding in the Hermitian scope by interfacing with topological physics. A single non-Hermitian band can host nontrivial topology that is defined over the nonzero windings of the system's eigenvalues, but not the eigenvectors, as opposed to the Hermitian topological systems. This unique non-Hermitian band topology is responsible for the intriguing non-Hermitian skin effect. Here, we show that the band topology of non-Hermitian one-band models can experience multiple phase transitions. Each transition is identified by a change of the eigenvalue winding. Such an interesting phenomenon is enabled by strategically manipulating the long-range couplings. Associated with the multiple phase transitions, the non-Hermitian skin effect exhibits anomalous behaviors, i.e., in different phases, the skin modes take on different forms of wave localizations. At the transition points, the skin modes evolve into Bloch-wavelike extended states, as if the Hermiticity is restored. For demonstration, we consider a modified Hatano-Nelson model with nonreciprocal next-nearest neighbor couplings. Therein, two phase transitions are identified, corresponding to a stationary and a dynamic one (with respect to the reciprocal nearest-neighbor coupling). Exact analytical derivations are performed to analyze the phase transitions and the associated anomalous non-Hermitian skin effect, which show consistency with the numerical results based on the generalized Brillouin zone method. Our work reveals rich non-Hermitian topological physics in one-band systems, which are considered to be topologically trivial in Hermitian systems. By further showing the anomalous non-Hermitian skin effect, intriguing wave manipulations may inspire experiments in classical realms such as photonics and phononics where versatile non-Hermitian controls are feasible.

Controlling Superhydrophobicity and Oleophobicity of Polydimethylsiloxane-Coated Silica Hybrid Particles

Hierarchical functional organic-inorganic hybrid particles for versatile control of surface wettability have attracted much attention in a wide range of applications from makeup cosmetics to anti-smudging optoelectronic devices. In this study, superhydrophobic and oleophobic organic-inorganic hybrid particles were prepared by a simple and systematic fabrication strategy using the synergistic combination of commonly available silica particles and polydimethylsiloxanes (PDMSs) with hydrophobic chain ends. Various types of PDMSs with different chain lengths and chemical structures were surface-grafted to silica microparticles through facile physical dispersion and subsequent thermal treatment to form hydrogen bonds or covalent bonds between the inorganic silica and organic PDMS polymers and thus induce a core-shell structure for the hybrid particles, which imparts superhydrophobicity and oleophobicity to the surface of silica particles. The prepared PDMS-coated silica hybrid particles with long PDMS chains exhibited a water contact angle of 151.2° and an oil contact angle of 15.2° due to the rough surface morphology and hydrophobic long-chain effects. Furthermore, the resulting organic-inorganic hybrid particles were thermally stable up to 420 °C. This controlled approach endowed the organic-inorganic hybrid particles with both superhydrophobic and oleophobic surfaces and, therefore, these particles were proven to be suitable for waterproof applications.

Tunable metasurfaces for seismic Love wave manipulation: A theoretical study

Seismic Love waves are horizontally polarized surface waves propagating within an overlying layer, which have been shown to pose potential hazards to infrastructures. In this study, we propose an original analytical formulation to investigate the interaction between seismic Love waves and a metasurface that is composed of a cluster of tunable anti-plane resonators. The formulation utilizes the Green's function of a layered half-space subjected to a surface SH source, to describe both the source-induced incident field and the resonator-excited scattered field. Based on the multiple scattering theory, we obtain the total wavefield of the layered half-space equipped with surface resonators by coupling the incident field and the scattered field. Besides, a closed-form dispersion relation governing the hybrid Love waves is derived by utilizing the effective medium approximation. We demonstrate the capabilities of our analytical formulation by modelling Love waves propagating across a pair and a cluster of resonators, evidenced by some complex phenomena (e.g., surface-to-bulk wave conversion and higher-order hybridized surface modes). The hybridization features of different Love modes and metasurface resonances are clearly revealed. We anticipate the proposed tunable metasurface and the formulation can shed light on versatile control of Love wave propagation.

Ultrabroadband Multichannel Vector Vortex Beams With Versatile Electrically Induced Functionality

AbstractThe emergence of vector vortex beams (VVBs) has opened new avenues for various applications in optics and photonics. However, owing to the formidable phase aberration ascribed to the chromatic dispersion, the generation of VVBs suffers from a limited working spectrum, thus rendering the massive integration level and functionality challenging. Here, this work proposes a creative paradigm to generate ultrabroadband multichannel VVBs, via programming the electric field vector through the twisted nematic liquid crystals configured by photopatterning. It is experimentally demonstrated the multichannel VVBs propagate along a group of diffraction orders among an unprecedented bandwidth over 1000 nm covering the visible and NIR band, and the working spectrum can be extended into the mid‐IR region even at 10 µm wavelength with a sufficient efficiency of more than 80%. Remarkably, distinct from the usual electrical switching on–off cycle, the multichannel VVBs can be optionally regulated in either a reversible or irreversible manner by conveniently adjusting the applied voltage, thus endowing the versatile functionality for smart control and confidential purposes. The combination of multichannel VVB generation, ultrabroad spectral range, versatile controllability, and simplicity renders the methodology quite promising in photonics, quantum science, and fundamental physics.

Utilizing the power controller, enhance the operation of a single-phase AC to DC converter

<span lang="EN-US">Smooth switching technology with a single-phase converter from AC to DC is existing in this work. A study of implementing a buck-batch converter was explored and the implementation details assessed. The system explaining the versatile balanced power control (VPBC) has advantages, the suggested boost buck processor is charged during the downtime; the voltage is relieved via the MOSFET switch. It has enhanced the power factor to 0.9715 at full load in further development. The advanced model of the AC to DC converter design will maintain stability and its reliability will depend on the average “charge” and “discharge” with the help of the VPBC-controlled current of the inductor, compensate automatically. Because of this process, a linear construction between line current and voltage is achieved by running normal work at regular intervals. As a result, they almost realized the PF at the input source. The output voltage of the planned for any load condition in the transformer model is always constant (0-1,000) watts. Suggested circuit has a great dynamic reaction. Suggested PFC circuit is usable for a range of loads. From the simulation, the efficiency of the suggested transformer is 91.11% upper at the rated load. Designed by MATLAB.</span>

The future technological potential of hydrogen fuel cell systems for aviation and preliminary co-design of a hybrid regional aircraft powertrain through a mathematical tool

The growing demand for air travel in the commercial sector leads to an increase in global emissions, whose mitigation entails transitioning from the current fossil-fuel based generation of aircrafts to a cleaner one within a short timeframe. The use of hydrogen and fuel cells has the potential to reach zero emissions in the aerospace sector, provided that required innovation and research efforts are substantially accomplished. Development programs, investments and new regulations are needed for this technology to be safe and economical. In this context, it makes sense to develop a model-based preliminary design methodology for a hybrid regional aircraft assisted by a battery hybridized fuel cell powertrain. The technological assumptions underlying the study refer to both current and expected data for 2035. The major contribution of the proposed methodology is to provide a mathematical tool that considers the interactions between the choice of components in terms of installed power and energy management. This simultaneous study is done because of the availability of versatile control maps. The tool was then deployed to define current and future technological scenarios for fuel cell, battery and hydrogen storage systems, by quickly adapting control strategies to different sizing criteria and technical specifications. In this way, it is possible to facilitate the estimation of the impact of different sizing criteria and technological features, at the aircraft level, on the onboard electrical system, the management of in-flight power, the propulsion methods, the impact of the masses on consumption and operational characteristics in a typical flight mission. The proposed combination of advanced sizing and energy management strategies allowed meeting mass and volume constraints with state-of-the-art PEM fuel cell and Li-ion battery specifications. Such a solution corresponds to a high degree of hybridization between the fuel cell system and battery pack (i.e., 300 kW and 750 kWh), whereas projected 2035 specs were demonstrated to help reduce mass and volume by 23 % and 40 %, respectively.

MicroFPGA: An affordable FPGA platform for microscope control

Modern microscopy relies increasingly on microscope automation to improve throughput, ensure reproducibility or observe rare events. Automation requires computer control of the important elements of the microscope. Furthermore, optical elements that are usually fixed or manually movable can be placed on electronically-controllable elements. In most cases, a central electronics board is necessary to generate the control signals they require and to communicate with the computer. For such tasks, Arduino microcontrollers are widely used due to their low cost and programming entry barrier. However, they are limiting in their performance for applications that require high-speed or multiple parallel processes. Field programmable gate arrays (FPGA) are the perfect technology for high-speed microscope control, as they are capable of processing signals in parallel and with high temporal precision. While plummeting prices made the technology available to consumers, a major hurdle remaining is the complex languages used to configure them. In this work, we used an affordable FPGA, delivered with an open-source and friendly-to-use programming language, to create a versatile microscope control platform called MicroFPGA. It is capable of synchronously triggering cameras and multiple lasers following complex patterns, as well as generating various signals used to control microscope elements such as filter wheels, servomotor stages, flip-mirrors, laser power or acousto-optic modulators. MicroFPGA is open-source and we provide online Micro-Manager, Java, Python and LabVIEW libraries, together with blueprints and tutorials.

A Self-Powered FBRJT AC-DC Conversion Circuit for Piezoelectric Energy Harvesting Systems

In this study, a complete model for a miniature excitation-powered piezoelectric generator (PG), analysis modes of operation and control of a full-bridge joule thief (FBRJT) circuit to identify the optimal points were investigated. The proposed model revealed the PG’s power dependency on mechanical excitation, acceleration, and frequency and defined the load behaviour for power optimisation. The proposed circuit, namely FBRJT, was integrated with the conventional full-bridge rectifier (FBR) in Stage 1 for AC-DC conversion and with the joule thief circuit in Stage 2 for DC-DC conversion. This integration acted as a boost converter without utilising the duty cycles and additional switching components. The electrical nature of the input of FBRJT with a simple structure, sensor-less control and auxiliary circuits showed a consistent agreement with the investigated testing scenarios using both ideal and impedance power sources. Additionally, the performance of the proposed circuit was also verified against the published results of power electronics circuits. The developed versatile circuit and control system can be utilised for many applications, such as mobile battery charging and energy harvesting.

Multilayered optofluidics for sustainable buildings

Indoor climate control is among the most energy-intensive activities conducted by humans. A building facade that can achieve versatile climate control directly, through independent and multifunctional optical reconfigurations, could significantly reduce this energy footprint, and its development represents a pertinent unmet challenge toward global sustainability. Drawing from optically adaptive multilayer skins within biological organisms, we report a multilayered millifluidic interface for achieving a comprehensive suite of independent optical responses in buildings. We digitally control the flow of aqueous solutions within confined milliscale channels, demonstrating independent command over total transmitted light intensity (95% modulation between 250 and 2,500 nm), near-infrared-selective absorption (70% modulation between 740 and 2,500 nm), and dispersion (scattering). This combinatorial optical tunability enables configurable optimization of the amount, wavelength, and position of transmitted solar radiation within buildings over time, resulting in annual modeled energy reductions of more than 43% over existing technologies. Our scalable "optofluidic" platform, leveraging a versatile range of aqueous chemistries, may represent a general solution for the climate control of buildings.

Graded-azimuthal-index fiber as a control element for radial-index and orbital-angular-momentum modes of Laguerre-Gaussian beams

We propose an azimuthally varying graded-index fiber that can efficiently create and control a definite set of radial-index and orbital-angular-momentum (OAM) modes of Laguerre-Gaussian beams and their superpositions. A rigorous coupled-wave analysis formalism is developed, which provides a ready analysis for the azimuthal-refractive-index variation in the Laguerre-Gaussian basis. In particular, we present effective control in the generation and coupling of the various OAM modes, including radial-index modes of the Laguerre-Gaussian beam within the fiber, wherein the propagation length of the fiber and the wavelength act as the control parameters. We further present the possibility of switching every alternate channel in a wavelength division multiplexing protocol to a higher-order spatial mode within the optical fiber to substantially reduce interchannel crosstalk. The graded azimuthal index fiber can be utilized in high-speed fiber-optic communications as a versatile control element for OAM modes and the radial-index mode of the Laguerre-Gaussian beam transformation.

Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams

1D spin-wave conduits are envisioned as nanoscale components of magnonics-based logic and computing schemes for future generation electronics. À-la-carte methods of versatile control of the local magnetization dynamics in such nanochannels are highly desired for efficient steering of the spin waves in magnonic devices. Here, we present a study of localized dynamical modes in 1-upmum-wide permalloy conduits probed by microresonator ferromagnetic resonance technique. We clearly observe the lowest-energy edge mode in the microstrip after its edges were finely trimmed by means of focused Ne^+ ion irradiation. Furthermore, after milling the microstrip along its long axis by focused ion beams, creating consecutively sim50 and sim100 nm gaps, additional resonances emerge and are attributed to modes localized at the inner edges of the separated strips. To visualize the mode distribution, spatially resolved Brillouin light scattering microscopy was used showing an excellent agreement with the ferromagnetic resonance data and confirming the mode localization at the outer/inner edges of the strips depending on the magnitude of the applied magnetic field. Micromagnetic simulations confirm that the lowest-energy modes are localized within sim15-nm-wide regions at the edges of the strips and their frequencies can be tuned in a wide range (up to 5 GHz) by changing the magnetostatic coupling (i.e., spatial separation) between the microstrips.

Trajectory-controlled high-order harmonic generation in ZnO crystals.

We experimentally and theoretically study high-order harmonic generation in zinc oxide crystals irradiated by mid-infrared lasers. The trajectories are mapped to the far field spatial distribution of harmonics. The divergence angles of on-axis and off-axis parts exhibit different dependences on the order of the harmonics. This observation can be theoretically reproduced by the coherent interference between the short and long trajectories with dephasing time longer than 0.5 optical cycle. Further, the relative contribution of the short and long trajectories is demonstrated to be accurately controlled by a one-color or two-color laser on the attosecond time scale. This work provides a reliable method to determine the electron dephasing time and demonstrates a versatile control of trajectory interference in the solid high-order harmonic generation.

Transport control of a swivel crane based on a vibration-less trajectory (A versatile control strategy)

Transport control of a swivel crane based on a vibration-less trajectory (A versatile control strategy)

Using molecules as a quantum interface to store ultrashort optical vortices

We exploit gas-phase molecules as light-matter interface to store an orbital angular momentum (OAM) or a superposition of OAM states (OAM-based photonic qubits) carried by ultrashort laser pulses. The interplay between spin angular momentum and OAM is exploited to encode the amplitude and spatial phase information of light beams into rotational coherences of molecules. This last is restored on-demand over tens of picoseconds with a reading beam by taking advantage of field-free molecular alignment. The underlying mechanism at the origin of the storage can be interpreted by the spatial structuring of the molecular sample induced by the field. The excitation indeed produces an inhomogeneous spatial distribution of molecular alignment (amplitude & orientation) whose periodical revivals associated with the quantum beatings of the rotational wavepacket enables to restore the spatial beam structure on-demand. The strategy is successfully demonstrated in CO2 molecules at room temperature. Besides applicability as storage medium with THz bandwidth application, the use of molecules as light-matter interface opens new functionalities in terms of optical processing and versatile control of OAM fields.

Design of nano-spintronics beamline at 3-GeV next-generation synchrotron radiation facility, NanoTerasu

A synchrotron radiation beamline in the soft- and tender-X ray energy range of 180-3000 eV with versatile polarization control has been designed for NanoTerasu, the 3-GeV next-generation synchrotron radiation facility at Tohoku, Japan. A series of four APPLE-II type undulators is adopted as a photon source to realize the required beam properties with high-speed polarization switching. The beamline optics is designed for a highly efficient and precise use of x-ray magnetic circular/linear dichroism (XMCD/XMLD) technique balancing high photon flux and energy resolution. The simulated performance of the segmented undulator together with the monochromator optics achieved the sufficiently high flux and energy resolution (E/ΔE) in whole target energy range. Two endstations with the different re-focus optics, one for marginal spot size with high flux and the other for ultimate focus down to ∼10 nm are also designed. The simulated performance of the beamline encourages the future researches of high-throughput and nm-focused spintronic measurements.

Modified Spatially Confined Strategy Enabled Mild Growth Kinetics for Facile Growth Management of Atomically-Thin Tungsten Disulfides.

Chemical vapor deposition (CVD) has been widely used to produce high quality 2D transitional metal dichalcogenides (2D TMDCs). However, violent evaporation and large diffusivity discrepancy of metal and chalcogen precursors at elevated temperatures often result in poor regulation on X:M molar ratio (M = Mo, W etc.; X = S, Se, and Te), and thus it is rather challenging to achieve the desired products of 2D TMDCs. Here, a modified spatially confined strategy (MSCS) is utilized to suppress the rising S vapor concentration between two aspectant substrates, upon which the lateral/vertical growth of 2D WS2 can be selectively regulated via proper S:W zones correspond to greatly broadened time/growth windows. An S:W-time (SW-T) growth diagram was thus proposed as a mapping guide for the general understanding of CVD growth of 2D WS2 and the design of growth routes for the desired 2D WS2 . Consequently, a comprehensive growth management of atomically thin WS2 is achieved, including the versatile controls of domain size, layer number, and lateral/vertical heterostructures (MoS2 -WS2 ). The lateral heterostructures show an enhanced hydrogen evolution reaction performance. This study advances the substantial understanding to the growth kinetics and provides an effective MSCS protocol for growth design and management of 2D TMDCs.

Two-dimensional lattice soliton and pattern formation in a cold Rydberg atomic gas with nonlocal self-defocusing Kerr nonlinearity

We propose a Rydberg-dressed atomic gas under the condition of electromagnetically induced transparency (EIT) to realize two-dimensional (2D) optical lattices and achieve nonlocal giant Kerr nonlinearity. We obtain the formation of stable 2D bright lattice solitons that result by the balance of diffraction with negative effective mass and nonlocal self-defocusing Kerr nonlinearity. Moreover, extended optical pattern formations are observed based on the modulation instability (MI). It is interesting to note that the solitons and patterns obtained are strongly influenced by the depth of the potential, the degree of nonlocality, and the strength of the Kerr nonlinearity. The results of our work provide a route for versatile control of laser patterns and solitons, which may have potential applications in optical communications and information processing.

Molecular Quantum Interface for Storing and Manipulating Ultrashort Optical Vortex

AbstractLight beams carrying orbital angular momentum (OAM) have become over the past few years a subject of widespread interest with unprecedented applications in various fields such as optical communication, super‐resolution imaging, optical tweezers, or quantum processing. In the present work it is demonstrated that gas‐phase molecules can be used as a quantum interface to store an OAM carried by an ultrashort laser pulse. The interplay between spin angular momentum and OAM is exploited to encode the spatial phase information of light beams into rotational coherences of molecules. The embedded spatial structure is restored on‐demand with a reading beam by taking advantage of field‐free molecular alignment. The strategy is successfully demonstrated in CO2 molecules at room temperature. Apart from applications to broadband coherent buffer memory, this method opens new functionalities in terms of optical processing and versatile control of OAM fields as well as for a deeper understanding of their role on various molecular processes.