Precise Phase Control Research Articles

Programmable metasurface based phase-modulating reflector for 2.4GHz wireless communications

Abstract This paper presents an innovative programmable metasurface structure that achieves precise phase control within the 2 to 2.7 GHz frequency range by adjusting the state of varactor diodes embedded in the unit cells. The design employs a single diode, which simplifies the structure, reduces manufacturing costs, and minimizes reflection loss. At 2.4 GHz, the metasurface achieves 1-bit phase responses of 0° and 180°, with a reflection amplitude exceeding 0.72, demonstrating excellent reflective performance. Moreover, as the 2.4 GHz frequency is closely related to wireless communication bands, this programmable metasurface shows significant potential in the field of wireless communication encryption. By integrating dual varactor diodes, the design enables 2-bit phase control with reflection phase angles of 0°, 90°, 180°, and 270°. To validate the design, a 1-bit metasurface structure was fabricated and tested, with experimental results showing a high degree of consistency with simulations, highlighting the potential of this structure in enhancing wireless communication security.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Moth-wing-inspired metasurface for modulating sound amplitude and phase

Moth wings are multifunctional bio-composite structures serve varied purposes, including sound absorption and flight. Inspired by this, we propose a metasurface for reflective acoustic wave modulation. The metasurface features periodically arranged resonant elements, consisting of perforated plates and resonant cavities, mimicking moth wing scales. The hinged connection between the resonant elements and the background structure allows for precise and wide-range tuning of sound amplitude and phase, and enables deployment on irregular surfaces. We present three detailed metasurface designs, showcasing various structural parameters to demonstrate their quantitative manipulation of sound amplitude and phase, both individually and simultaneously. In addition to conventional energy absorption and path manipulation functions, the metasurface also highlights several striking features, including wavefront tailoring and reflection shunting, as demonstrated through numerical simulations. This study offers novel insights into the precise control of wave amplitude and phase over diverse scales and terrains, whilst also presenting a practical implementation in the field of acoustics.

Phase-resolved measurement and control of ultrafast dynamics in terahertz electronic oscillators

As a key component for next-generation wireless communications (6 G and beyond), terahertz (THz) electronic oscillators are being actively developed. Precise and dynamic phase control of ultrafast THz waveforms is essential for high-speed beam steering and high-capacity data transmission. However, measurement and control of such ultrafast dynamic process is beyond the scope of electronics due to the limited bandwidth of the electronic equipment. Here we surpass this limit by applying photonic technology. Using a femtosecond laser, we generate offset-free THz pulses to phase-lock the electronic oscillators based on resonant tunneling diode. This enables us to perform phase-resolved measurement of the emitted THz electric field waveform in time-domain with sub-cycle time resolution. Ultrafast dynamic response such as anti-phase locking behaviour is observed, which is distinct from in-phase stimulated emission observed in laser oscillators. We also show that the dynamics follows the universal synchronization theory for limit cycle oscillators. This provides a basic guideline for dynamic phase control of THz electronic oscillators, enabling many key performance indicators to be achieved in the new era of 6 G and beyond.

Control of multi-modal scattering in a microwave frequency comb

Control over the coupling between multiple modes of a frequency comb is an important step toward measurement-based quantum computation with a continuous-variable system. We demonstrate the creation of square-ladder correlation graphs in a microwave comb with 95 modes. The graphs are engineered through precise control of the relative phase of three pumps applied to a Josephson parametric oscillator. Experimental measurement of the mode scattering matrix is in good agreement with theoretical predictions based on a linearized equation of motion of the parametric oscillator. The digital methods used to create and measure the correlations are easily scaled to more modes and more pumps, with the potential to tailor a specific correlation graph topology.

Reconfigurable metasurface array for diverse retrodirective reflections and radar cross section reduction

Abstract Retroreflectors can scatter the arbitrarily incident wave back to incoming direction, demonstrating great potential in wireless communication. However, there are limitations in adaptive retroreflection and polarization modulation with the existing retroreflectors. In this paper, a novel metasurface array with a reconfigurable transmission line (TL) network has been proposed to flexibly achieve multiple manipulation functions of electromagnetic wave including upper half-space cross-polarized retroreflection and circularly polarized retroreflection in the diagonal planes and radar cross section (RCS) reduction. To accomplish these capabilities, a novel transmission mode for ferrite circulators has been developed, enabling precise phase control of the TL. By adjusting the operation states of the circulators, multiple phase differences between forward and reverse transmission directions including ±90° and ±180° are generated. With the obtained phase differences, the metasurface array can flexibly achieve the adaptive retroreflection fields with multiple polarization characteristics based on the spatial field superposition and the RCS reduction based on the phase cancellation. To validate the concept and feasibility of the proposed reconfigurable retrodirective metasurface, an X-band prototype has been fabricated and measured. Good agreement between the simulation and the experiment is observed to verify the effectiveness of our retrodirective design in upper half-space wave manipulation.

High-Performance Piezoelectric Nanogenerator Based on Odd–Odd Nylon Nanofibers for Wearable Electronics via Precise Control of Ferroelectric Phase and Orientation

High-Performance Piezoelectric Nanogenerator Based on Odd–Odd Nylon Nanofibers for Wearable Electronics via Precise Control of Ferroelectric Phase and Orientation

A Low-Loss Passive D-Band Phase Shifter for Calibration-Free, Precise Phase Control

A Low-Loss Passive <i>D</i>-Band Phase Shifter for Calibration-Free, Precise Phase Control

Ultrafast state-selective tunneling in two-dimensional semiconductors with a phase- and amplitude-controlled THz-scanning tunneling microscope

THz-pulse driven scanning tunneling microscopy (THz-STM) enables access to the ultrafast quantum dynamics of low-dimensional material systems at simultaneous ultrafast temporal and atomic spatial resolution. State-selective tunneling requires precise amplitude and phase control of the THz pulses combined with quantitative near-field waveform characterization. Here, we employ our state-of-the-art THz-STM with multi-MHz repetition rates, efficient THz generation, and precisely tunable THz waveforms to investigate a single sulfur vacancy in monolayer MoS2. We demonstrate that 2D transition metal dichalcogenides (TMDs) are an ideal platform for near-field waveform sampling by THz cross-correlation. Furthermore, we determine the THz voltage via QEV scans, which measure the THz rectified charge Q as a function of THz field amplitude E and dc bias Vdc. Mapping the complex energy landscape of localized states with a resolution down to 0.01 electrons per pulse facilitates state-selective tunneling to the HOMO and LUMO orbitals of a charged sulfur vacancy.

Observation of parity-time symmetry in diffusive systems.

Phase modulation has scarcely been mentioned in diffusive physical systems because the diffusion process does not carry the momentum like waves. Recently, non-Hermitian physics provides a unique perspective for understanding diffusion and shows prospects in thermal phase regulation, exemplified by the discovery of anti-parity-time (APT) symmetry in diffusive systems. However, precise control of thermal phase remains elusive hitherto and can hardly be realized, due to the phase oscillations. Here we construct the PT-symmetric diffusive systems to achieve the complete suppression of thermal phase oscillation. The real coupling of diffusive fields is readily established through a strong convective background, and the decay-rate detuning is enabled by thermal metamaterial design. We observe the phase transition of PT symmetry breaking with the symmetry-determined amplitude and phase regulation of coupled temperature fields. Our work shows the existence of PT symmetry in dissipative energy exchanges and provides unique approaches for harnessing the mass transfer of particles, wave dynamics in strongly scattering systems, and thermal conduction.

Electro-optic tuning in composite silicon photonics based on ferroionic 2D materials

Tunable optical materials are indispensable elements in modern optoelectronics, especially in integrated photonics circuits where precise control over the effective refractive index is essential for diverse applications. Two-dimensional materials like transition metal dichalcogenides (TMDs) and graphene exhibit remarkable optical responses to external stimuli. However, achieving distinctive modulation across short-wave infrared (SWIR) regions while enabling precise phase control at low signal loss within a compact footprint remains an ongoing challenge. In this work, we unveil the robust electro-refractive response of multilayer ferroionic two-dimensional CuCrP2S6 (CCPS) in the near-infrared wavelength range. By integrating CCPS into silicon photonics (SiPh) microring resonators (MRR), we enhance light-matter interaction and measurement sensitivity to minute phase and absorption variations. Results show that electrically driven Cu ions can tune the effective refractive index on the order of 2.8 × 10−3 RIU (refractive index unit) while preserving extinction ratios and resonance linewidth. Notably, these devices exhibit low optical losses and excellent modulation efficiency of 0.25 V.cm with a consistent blue shift in the resonance wavelengths among all devices for either polarity of the applied voltage. These results outperform earlier findings on phase shifters based on TMDs. Furthermore, our study demonstrates distinct variations in electro-optic tuning sensitivity when comparing transverse electric (TE) and transverse magnetic (TM) modes, revealing a polarization-dependent response that paves the way for diverse applications in light manipulation. The combined optoelectronic and ionotronic capabilities of two-terminal CCPS devices present extensive opportunities across several domains. Their potential applications range from phased arrays and optical switching to their use in environmental sensing and metrology, optical imaging systems, and neuromorphic systems in light-sensitive artificial synapses.

Expanding the bandwidth of fluorescence-detected two-dimensional electronic spectroscopy using a broadband continuum probe pulse pair.

We demonstrate fluorescence-detected two-dimensional electronic spectroscopy (F-2DES) with a broadband, continuum probe pulse pair in the pump-probe geometry. The approach combines a pump pulse pair generated by an acousto-optic pulse-shaper with precise control of the relative pump pulse phase and time delay with a broadband, continuum probe pulse pair created using the Translating Wedge-based Identical pulses eNcoding System (TWINS). The continuum probe expands the spectral range of the detection axis and lengthens the waiting times that can be accessed in comparison to implementations of F-2DES using a single pulse-shaper. We employ phase-cycling of the pump pulse pair and take advantage of the separation of signals in the frequency domain to isolate rephasing and non-rephasing signals and optimize the signal-to-noise ratio. As proof of principle, we demonstrate broadband F-2DES on a laser dye and bacteriochlorophyll a.

Increasing Mass Transfer Resistance of MOFs as a Reverse Tuning Strategy to Achieve High-Resolution Gas Chromatographic Separation.

In separation science, precise control and regulation of the MOF stationary phase are crucial for achieving a high separation performance. We supposed that increasing the mass transfer resistance of MOFs with excessive porosity to achieve a moderate mass transfer resistance of the analytes is the key to conducting the MOF stationary phase with a high resolution. Three-dimensional UiO-67 (UiO-67-3D) and two-dimensional UiO-67 (UiO-67-2D) were chosen to validate this strategy. Compared with UiO-67-3D with overfast mass transfer and low retention, the reduced porosity of UiO-67-2D increased the mass transfer resistance of analytes in reverse, resulting in improved separation performance. Kinetic diffusion experiments were conducted to verify the difference in mass transfer resistance of the analytes between UiO-67-3D and UiO-67-2D. In addition, the optimization of the UiO-67-2D thickness for separation revealed that a moderate diffusion length of the analytes is more advantageous in achieving the equilibrium of absorption and desorption.

The relationship between fuel reactivity and exergy features in combustion process

Fuel reactivity is a flexible and feasible method to control combustion, thus reactivity-controlled compression ignition (RCCI) has the potential to achieve lower emissions and higher thermal efficiency. However, the exergy loss during combustion hinders the further exergy-work transform, which limits the thermal efficiency further improvement. The present work focuses on the relationship between fuel reactivity and exergy which contains exergy loss (EL) and thermomechanical exergy (Exthermo due to the temperature and pressure imbalance between system and reference state). By varying the reactivity of primary reference fuels (PRFs) with different initial boundary conditions, it is found that different PRFs could not reduce EL and change Exthermo under same condition but could change the exergy loss rate as well as the EL structure by influencing low-temperature combustion. In terms of boundary conditions, both high temperature and lean mixture could improve Exthermo but with different mechanism: high temperature saving EL into Exthermo, lean mixture recovering incomplete combustion exergy (Exincom) into Exthermo. By contrast, equivalence ratio more easily affects EL and Exthermo. In three-dimensional situation, it is found that decreasing reactivity of PRFs leads more in-cylinder area below equivalence ratio 1.0 which benefits for the Exthermo improvement, but it would cause Exthermo structure mutation which is unfriendly for the smooth output of work near top dead center. The conversion of fuel exergy to final useful work is indirect, and there exist two sub-processes: fuel exergy to thermomechanical exergy then thermomechanical exergy to useful work. The final exergy-work transform efficiency is influenced by both processes. Therefore, using low reactivity fuel as PRF90 in engine is favor of the exergy from fuel transforming into Exthermo by more lean mixture, adopting high reactivity fuel as PRF0 is favor of the Exthermo sequential structure which is benefit for the combustion control and useful work extract near top dead center. Therefore, there is potential to further improve the thermal efficiency by using a dual-fuel combination, with the low reactivity fuel creating a low equivalence ratio region to improve the thermomechanical exergy, and the high reactivity fuel achieving precise phase control during the combustion.

Deep neural network-based phase calibration in integrated optical phased arrays

Calibrating the phase in integrated optical phased arrays (OPAs) is a crucial procedure for addressing phase errors and achieving the desired beamforming results. In this paper, we introduce a novel phase calibration methodology based on a deep neural network (DNN) architecture to enhance beamforming in integrated OPAs. Our methodology focuses on precise phase control, individually tailored to each of the 64 OPA channels, incorporating electro-optic phase shifters. To effectively handle the inherent complexity arising from the numerous voltage set combinations required for phase control across the 64 channels, we employ a tandem network architecture, further optimizing it through selective data sorting and hyperparameter tuning. To validate the effectiveness of the trained DNN model, we compared its performance with 20 reference beams obtained through the hill climbing algorithm. Despite an average intensity reduction of 0.84 dB in the peak values of the beams compared to the reference beams, our experimental results demonstrate substantial agreements between the DNN-predicted beams and the reference beams, accompanied by a slight decrease of 0.06 dB in the side-mode-suppression-ratio. These results underscore the practical effectiveness of the DNN model in OPA beamforming, highlighting its potential in scenarios that necessitate the intelligent and time-efficient calibration of multiple beams.

Improvement of terahertz beam modulation efficiency for baseless all-dielectric coded gratings

Optical metasurfaces are two-dimensional ultrathin devices based on single-layer or multilayer arrays of subwavelength nanostructures. They can achieve precise control of phase, amplitude, and polarization on the subwavelength scale. In this paper, a substrate-free all-silicon coded grating is designed, which can realize the phase control of the outgoing beam after the y-polarized plane wave is vertically incident on the metasurface at 0.1 THz. Through a single-layer silicon nanoarray structure, a low-reflection anomalous transmission metasurface is realized, and a variety of different beam deflectors are designed based on these encoded gratings. We propose a coded grating addition principle, which adds and subtracts two traditional coded grating sequences to obtain a new coded grating sequence. The encoded supergrating can flexibly control the scattering angle, and the designed substrate-free all-silicon encoded grating can achieve a deflection angle of 48.59°. In order to verify the principle of coded grating addition, we experimented with cascade operation of two coded sequence gratings to obtain the flexible control of the terahertz beam of the composite supergrating. The principle of grating addition provides a new degree of freedom for the flexible regulation of the terahertz wavefront. At the same time, this method can be extended to the optical band or microwave band, opening up new ways for electromagnetic wave manipulation and beam scanning.

An optical investigation on the effects of split-injection on hydrogenated catalytic biodiesel/gasoline dual-fuel engine under cold start conditions

Reactivity-controlled compression ignition (RCCI) mode has emerged as a promising technology for internal combustion engines, offering precise combustion phase control and the potential to meet stringent emission regulations. However, RCCI mode faces challenges, particularly misfiring during cold start conditions. This study proposes a solution by utilizing hydrogenated catalytic biodiesel (HCB) as a pilot fuel for gasoline and implementing a split-injection strategy to address the challenge. Experimental research was conducted on an optical engine under cold start conditions, incorporating three split-injection strategies: P30M70 (30 % main-injection and 70 % pilot-injection), P50M50, and P70M30. The results demonstrate that although gasoline can only be ignited by the main-injected HCB under coldstart conditions, the in-cylinder environment becomes more dynamic due to the pilot-injection. Consequently, split-injection reduces ignition delay by up to 7.09 °CA and shortens the combustion stage compared to single-injection. Among the various injection strategies examined, P30M70 demonstrated outstanding in-cylinder heat release performance, surpassing other split-injection strategies by up to 26.77 J/CAD, and outperforming the single-injection by 22.94 J/CAD. Visualization tests indicate that applying the P30M70 strategy leads to higher soot production under conditions of delayed main-injection timing (-15 °CA ATDC). However, the peak flame area under cold-start conditions is 53.16 % greater than P50M50 and 71.28 % greater than P70M30, highlighting excellent flame propagation characteristics. The average in-cylinder temperature suggests that a larger visible flame area contributes to engine warming. Despite the inherent trade-off, the dual-fuel mode of HCB/gasoline proves suitable for RCCI engines, with the P30M70 split-injection strategy being recommended for the cold start stage.

Dynamic gravitational excitation of structural resonances in the hertz regime using two rotating bars

With the planning of new ambitious gravitational wave observatories, fully controlled laboratory experiments on dynamic gravitation become more and more important. Such experiments can provide new insights in potential dynamic effects such as gravitational shielding or energy flow and might contribute to bringing light into the mystery still surrounding gravity. Here we present a laboratory-based transmitter-detector experiment using two rotating bars as transmitter and a 42 Hz, high-Q bending beam resonator as detector. Using a precise phase control to synchronize the rotating bars, a dynamic gravitational field emerges that excites the bending motion with amplitudes up to 100 nm/s or 370 pm, which is a factor of 500 above the thermal noise. The two-bar design enables the investigation of different transmitter configurations. The detector movement is measured optically, using three commercial interferometers. Acoustical, mechanical, and electrical isolation, a temperature-stable environment, and lock-in detection are central elements of the setup. The moving load response of the detector is numerically calculated based on Newton’s law of gravitation via discrete volume integration, showing excellent agreement between measurement and theory both in amplitude and phase. The near field gravitational energy transfer is 1025 times larger than the one of the propagating gravitational wave component.

Time-resolved electron paramagnetic resonance spectrometer based on ultrawide single-sideband phase-sensitive detection.

A time-resolved electron paramagnetic resonance (TREPR) method with 40ns time resolution and a high sensitivity suitable for the detection of short-lived radicals under thermal equilibrium is developed. The key is the introduction of a new detection technique named ultrawide single sideband phase sensitive detection (U-PSD) to the conventional continuous-wave EPR, which remarkably enhanced the sensitivity for the detection of broadband transient signals compared with the direct detection protocol. By repeatedly triggering a transient kinetic event f(t) (e.g., by laser flash photolysis) under a 100kHz magnetic field modulation with precise phase control, this technique can build an ultrawide single sideband modulated signal. After single sideband demodulation, the flicker noise-suppressed signal f(t) with wide bandwidth is recovered. A U-PSD TREPR spectrometer prototype has been built, which integrated timing sequence control, laser flash excitation, data acquisition systems, and the U-PSD algorithm with a conventional continuous-wave EPR. It exhibited excellent performance in monitoring a model transient radical system, laser flash photolysis of benzophenone in isopropanol. Both the intense chemically induced dynamic electron polarization signals and the much weaker thermal equilibrium EPR signals of the generated acetone ketyl radical and benzophenone ketyl radical were clearly observed within a wide timescale ranging from sub-microsecond to milliseconds. This prototype validated the feasibility of the U-PSD technique and demonstrated its superior performance in studying complex photochemical systems containing various transient radicals, which complements the established TREPR techniques and provides a powerful tool for deep mechanistic understandings, such as in photoredox catalysis and artificial photosynthesis.