Reflection Phase Research Articles

MEMS-tunable topological bilayer metasurfaces for reconfigurable dual-state phase control

Tunable optical metasurfaces (MSs) have demonstrated exceptional capabilities in actively manipulating light fields. However, most existing tunable MSs are limited to controlling only one functionality. Here, by combining a MEMS mirror with a plasmonic bilayer MS (BMS), we develop an electrically driven MEMS-BMS platform enabling complete reflection phase transformation and switching between two encoded functionalities by actuating the MEMS mirror. This capability stems from different optical responses of each MS layer at distinct MEMS-BMS separations, due to evolving topological singularities in a defined parameter space. With this tunable topological MEMS-BMS platform, we demonstrate polarization-independent MEMS-BMS for reconfigurable diffraction gratings, achieving ∼25% efficiency, ∼0.75 contrast at 850-nm wavelength, and fast response (∼5µs). The MEMS-BMS arrangement for generating vortex beams with switchable topological charges of ±1 is also demonstrated, evidenced by distinct near- and far-field interferograms. Our work expands the scope of tunable MSs by exploiting dynamic topological phases in the MEMS-BMS arrangement, paving the way for multifunctional tunable meta-optics.

MICROWAVE REFLECTOMETRY CIRCUITS INTEGRATION WITH COAXIAL PROBE FOR INITIAL BREAST TUMOR DETECTION

A six-port reflectometry (SPR) system was developed to predict the dielectric properties of both tumor and normal breast tissue, intended for medical diagnostic applications. Ensuring precise measurements, the SPR underwent calibration using a well-established four-step procedure, which will be briefly outlined. Afterward, the investigated coaxial probe was connected to the SPR through the calibrated measurement port. Subsequently, the exposed end of the probe aperture was immersed into synthetic samples representing both healthy and cancerous breast tissue to assess the dielectric constant, εrʹ and loss factor, εrʺ across frequencies ranging from 1.5 GHz to 3.3 GHz. The dielectric constant, εrʹ and loss factor, εrʺ were derived from the measured reflection coefficient using a closed-form equation associated with the coaxial probe. An examination was undertaken to compare the performance of a commercially available vector network analyzer (VNA) outfitted with a Keysight 85070E dielectric probe against an SPR-probe system. The comparison was based on analyzing the reflection coefficient magnitude, phase shift, dielectric constant, and loss factor of synthetic breast tissue samples. The study revealed maximum absolute errors of 0.01, 1.07°, 1.12, and 0.75 for the measured reflection coefficient magnitude, phase shift, dielectric constant, and loss factor, respectively. The calibrated reflection coefficient and predicted relative permittivity, εr can be effectively utilized to distinguish between normal (εrʹ < 50) and tumor (εrʹ > 50) breast tissue.

Retrieving Estimates of the Storm‐Relative Wind Profile From the Vertical Variation of Hydrometeor Size Sorting Signatures

AbstractRaindrop fall speed increases with raindrop size. Because larger raindrops fall through a given layer of the atmosphere more quickly compared to smaller raindrops, they spend less time in the layer and, therefore, have less time to be acted on and advected by the storm‐relative winds. This results in hydrometeor size sorting which impacts the polarimetric radar variables such as differential reflectivity and specific differential phase . Previous work has shown a strong correlation between the mean storm‐relative wind in the sorting layer and the separation between regions of enhanced and at the bottom of the sorting layer. This study leverages this finding, along with a simple size sorting model, to construct radar‐derived estimates of the storm‐relative wind profile. The radar‐derived “pseudo‐hodographs” are well‐correlated with the magnitude and direction of the corresponding storm‐relative wind profiles. Further, these radar‐derived estimates of the storm‐relative winds are used to calculate estimates of shear and storm‐relative helicity, which also exhibit a strong correlation.

Design of polarization-independent multilayer dielectric gratings: a reflection-phase threaded approach

We present a method to design polarization-independent multilayer dielectric gratings. In this method the reflection phases in TE and TM polarizations of the multilayer stack thread surface-relief grating at the top and the multilayer stack at the bottom together, allowing the two parts first to be designed separately and efficiently, and then to be combined to achieve simultaneously high diffraction efficiency and large fabrication tolerance. We find numerically that in general a periodic stack is unable to provide the top-grating-demanded phase difference between TM and TE polarizations; adequate aperiodic layers atop of a periodic stack are needed. The analytic diffraction efficiency formula of a recent work [J. Opt. Soc. Am. A 41, 252 (2024)] is used at various places of the presented optimization algorithm to save computation time. An example grating with rectangular surface-relief profile and another with trapezoidal profile were successfully designed, validating the effectiveness of this design method.

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.

A hybrid equivalent circuit model and plane wave spectrum method for decoupling surface designs in multi‐band shared‐aperture antenna arrays

AbstractShared‐aperture antenna arrays are attractive for 5G base stations, owing to their compact size and multi‐band frequency coverage. Decoupling surfaces are effective for suppressing crossband mutual coupling. However, their designs typically rely on full‐wave simulations of scattering parameters, which may not ensure a good radiation performance and is time‐consuming. A systematic methodology based on the hybrid equivalent circuit model and plane wave spectrum method is proposed for decoupling surface designs. The decoupling surface is represented by its equivalent circuit and the spectral expression converts the electromagnetic field into a circuit problem. Both the scattering parameter and radiation pattern can be solved with the circuit, offering an efficient design method that ensures consistent radiation patterns between the model and full‐wave simulations. A double‐layer decoupling surface with wide stopbands, high transmission property, and sharp roll‐off transition was realised. Furthermore, to reduce the overall profile height, the reflection phase of the decoupling surface was tuned. A triple‐band shared‐aperture base station antenna array was developed. Simulated and measured results demonstrate the array works properly in the 0.69–0.96 GHz, 1.7–2.7 GHz, and 3.3–3.8 GHz frequency bands with stable radiation patterns, and crossband mutual coupling is well suppressed, validating the effectiveness of the proposed methodology.

High-Efficiency Microwave Wireless Power Transmission via Reflective Phase Gradient Metasurfaces and Surface Wave Aggregation.

Microwave Wireless Power Transfer (MWPT) technology is crucial for emergency power supply during natural disasters and powering off-grid equipment. Traditional antenna arrays, however, suffer from low energy capture efficiency, difficult impedance matching, complex synthetic networks, and intricate manufacturing processes. This paper introduces a microwave energy receiver design utilizing Reflective Phase Gradient Metasurfaces (R-PGMs) and surface wave energy convergence technology. The design leverages the effective plane wave-to-surface wave conversion capability of R-PGMs to transform incident microwave energy into a surface wave mode, which is then efficiently harvested using a circular energy convergence array before being output to a coupling port. By optimizing R-PGM parameters, an ideal 60° phase gradient distribution is achieved, facilitating the focus of surface wave energy via dispersion characteristics. These components are integrated into a hybrid antenna array, complemented by a matched energy output port structure. Numerical simulations show that this array can efficiently convert microwave energy from plane waves to surface waves, achieving a conversion efficiency of 85.32% and a collection efficiency of 68.26%. Experimental results corroborate these findings, with peak energy collection efficiency reaching 64.68% at 5.8 GHz and an RF-DC conversion efficiency of 42%, confirming the design's efficacy. Compared to conventional methods, this design simplifies the system by avoiding complex combining networks and significantly enhances the efficiency of microwave MWPT.

Reconfigurable Multifunctional Metasurfaces for Full-Space Electromagnetic Wave Front Control

In order to implement multiple electromagnetic (EM) wave front control, a reconfigurable multifunctional metasurface (RMM) has been investigated in this paper. It can meet the requirements for 6G communication systems. Considering the full-space working modes simultaneously, both reflection and transmission modes, the flexible transmission-reflection-integrated RMM with p-i-n diodes and anisotropic structures is proposed. By introducing a 45°-inclined H-shaped AS and grating-like micro-structure, the polarization conversion of linear to circular polarization (LP-to-CP) is achieved with good angular stability, in the transmission mode from top to bottom. Meanwhile, reflection beam patterns can be tuned by switching four p-i-n diodes to achieve a 1-bit reflection phase, which are embedded in the bottom of unit cells. To demonstrate the multiple reconfigurable abilities of RMMs to regulate EM waves, the RMMs working in polarization conversion mode, transmitted mode, reflected mode, and transmission-reflection-integrated mode are designed and simulated. Furthermore, by encoding two proper reflection sequences with 13×13 elements, reflection beam patterns with two beams and four beams can be achieved, respectively. The simulation results are consistent with the theoretical method. The suggested metasurface is helpful for radar and wireless communications because of its compact size, simple construction, angular stability, and multi-functionality.

Anisotropic hypocycloid inspired 3-bit digital coding metasurface for radar cross section reduction

Abstract Recently, researchers have realized various exotic electromagnetic (EM) control devices using the coded metasurfaces, sparking a broad investigation into the phase or amplitude-based encoding method, as well as their combination, in the field of metasurface design. In this paper, to evaluate the influence of random mutual coupling between the adjacent element on the scattering performance of metasurface, and also to minimize the backward radar cross section (RCS) of metal plate targets, a novel encoding approach combining the reflection phase and element-form has been proposed. During the implementation process, an anisotropic hypocycloid inspired 3-bit digital coding metasurface was designed. It consists of 9 different element-forms, with each capable of providing 7 phase states. Simulation results demonstrate that the random mutual coupling introduced by the proposed elements does not significantly affect the RCS performance of the metasurface. With a good polarization insensitivity property for both linearly and circularly polarized waves, the designed 3-bit digital coding metasurface can achieve more than 20 dB RCS reduction at 10 GHz, while simultaneously transmitting additional information by encoding the element forms. The good consistency between theoretical simulation and sample testing unequivocally validates the precision of the design, this paper may serve as a useful reference for expanding the design methods of metasurfaces.

A modified dumbbell-shaped highly efficient broadband multifunctional polarizer for X and Ku band applications

Abstract A novel metasurface offering polarization conversion characteristic in five bands is studied and developed in this paper. To provide the anisotropic feature to the structure, a diagonally placed tapered rod is combined with two semicircular stubs. Due to the controlling ability to convert horizontal to vertical polarization and vice versa, and linear to circular polarization (CP), it serves as a multifunctional polarization converter. Simulation results suggest that the proposed polarizer functions as cross polarizer over 4.74−5.12 and 9.12−13.48 GHz. Additionally, it exhibits a distinct type of rotational sense across 4.24−4.68, 5.24−8.64, and 13.72–15.14 GHz in its linear to CP conversion behavior. The axial ratio of the polarizer is well below 3 dB throughout overall CP bands due to the minimum tolerance level in reflection phases with respect to acceptable limits. Moreover, it is noticed that the sense of CP is left-handed in the first band while right-handed in the remaining two bands. Thus, the suggested polarizer has potential to be integrated with antennas for satellite, defense, industry applications for getting the desired type of polarization in the distinguished bands.

Wide-angle low-scattering transmitarray antenna based on transmit-reflect selective metasurface

Abstract A high-gain transmitarray antenna with low radar cross section (RCS) properties is presented in this paper. Compared with conventional high-profile multilayer designs, we introduce a transmit-reflect selective metasurface integrated with high-gain transmission and random scattering functions, achieving a reduced thickness of 0.13 λ 0 (where λ 0 is the wavelength at the center frequency). For the meta-atom design, we combine geometric rotation and dimension optimization to realize 1-bit independent transmit and reflection phase modulation, respectively. Moreover, in metasurface coding strategy, we employ an initial phase optimization method and a simulated annealing algorithm to determine the optimal coding matrices. The experimental results demonstrate high-performance radiation characterized by the peak gain of 23.6 dB, maximum aperture efficiency of 28.5%, and 3 dB gain bandwidth of 18.4%. For x-polarization, measured 10 dB RCS reduction bandwidth under transverse magnetic (TM) 0°-45° and transverse electric (TE) 0°-20° incidence are 9.02–11.36 GHz. For y-polarization, 10 dB RCS reduction bandwidth under TM 0–60° and TE 0–30° incidence is 8.82–10.96 GHz.

Universality of the Spectra of Multiterminal Josephson Junction

Andreev bound states are formed in multiterminal structures based on normal metals and superconductors. Their spectrum is determined by the system parameters, in particular the scattering phases and transmission coefficients at the nodes. The article found conditions under which Andreev bound states are universal: they don’t change with any change in the reflection phases. As a consequence, the spectrum is completely determined by the transport characteristics of the system. The result was obtained for a structure in the form of a normal metal M-finite star, each of the rays (terminals) Nk of which is in contact with its superconductor Sk, 1 ≤ k ≤ M. Together they form a multiterminal Josephson junction. At the center of the structure there is a non-magnetic impurity with its some scattering matrix.

Peningkatan Hasil Belajar Pendidikan Agama Katolik dan Budi Pekerti dengan Metode Problem Based Learning Fase D Kelas VII SMP Negeri 3 Tukka

This study aims to determine the improvement in student learning outcomes in Catholic Religious Education and Character Education after the implementation of the Problem Based Learning (PBL) method for seventh-grade students in Phase D at SMP Negeri 3 Tukka. The research method used is Classroom Action Research (CAR) conducted in two cycles. Each cycle consists of planning, implementation, observation, and reflection phases. This method was chosen for its ability to develop critical thinking skills, collaboration, and the application of religious values in daily life. The study employs a quantitative approach with pretests and posttests to measure learning outcomes. Data were collected from test results and observations during the learning process. The results indicate a significant improvement in student learning outcomes following the implementation of the PBL method. In the first cycle, the average student score increased from 70.6 to 75.6, while in the second cycle, it rose further to 90.6. Additionally, there was an improvement in critical thinking skills and the ability to work collaboratively among students. Thus, the implementation of the PBL method has proven effective in enhancing learning outcomes in Catholic Religious Education and Character Education for seventh-grade students in Phase D at SMP Negeri 3 Tukka.

1-bit absorption-diffusion acoustic coding metasurface

Acoustic metasurfaces demonstrate unprecedented potential for flexible capabilities of the acoustic wavefront manipulation. Especially, acoustic diffusers and absorbers via acoustic metasurfaces have garnered significant attention of researchers due to the excellent performance. However, although these diffusers and absorbers have achieved excellent acoustic scattering suppression, it still remains a significant challenge to obtain higher scattering suppression. Here, a 1-bit absorption-diffusion acoustic coding metasurface (ADM) is proposed, which can achieve high-performance acoustic backward scattering reduction in the operating frequency by combining the advantages of acoustic diffusers and absorbers. In order to realize the proposed ADM, two kinds of subwavelength dual-layer unit cells with opposite reflection phases and low amplitudes are introduced. Both simulated and experimental results demonstrate that the proposed ADM can achieve the pre-designed backward acoustic scattering reduction. The proposed integrated mechanism can provide a new method for designing high-performance acoustic metasurfaces, which can have potential applications in stealth technology, noise control and other relevant applications.

A novel broadband low backscattering antenna array based on integration of absorptive and coding metasurface

AbstractThis paper presents a low‐scattering 1 × 2 patch array antenna combining resistive and coding metasurfaces (MSs) for the reduction of wideband‐backscatter. An artificial magnetic conductor technology is used to validate the proposed technique, which is fundamentally based on scattering, phase cancellation, and absorptive property of the MS. By integration of coding MS elements and an absorbent unit cell, three different array blocks are utilized to significantly reduce the monostatic and bistatic backscattered energy level from 6.5 to 16.5 GHz, as well as overall reduction from 5 to 22 GHz. Under the incidence of plane waves, various reflection phases have been observed. The diffusion of the scattering energy from the surface can be achieved by carefully choosing the phase distributions for the reflected waves. Additionally, the bistatic backscattered energy level of the prototype is realized at various frequency points. This technique is validated using artificial magnetic conductors, which uniquely combine the effects of scattering, phase cancellation, and absorption in the MS's hybrid unit cells. Further, antenna array parameters are optimized for frequency, polarization, and angular diversity, S‐parameters, radiating efficiency, reducing radar cross section (RCS) in the wideband range and ensuring robust performance. The experimental results were substantiated by simulations of the reference and proposed prototypes suggesting that the proposed prototype can be a good candidate for applications that require a low monostatic and bistatic RCS platform.

A reflective approach to educational “design”

The purpose of this article is to offer a comprehensive outline of the intents, processes and results of a research, training and experimentation project which involved educators, teachers, pedagogists and external trainers. This project resulted in a long process of redefinition of a “design approach to education within a network of municipality-run infant-toddlers centres and preschools located within the Province of Reggio Emilia (IT). If we conceive “progettazione” (design) as a research-oriented approach, as an educational and training process in which the aspects of “progettazione”, action and evaluation constantly intertwine, “progettazione” turns into a strategy that sustains the collaborative construction of the knowledge of both adults and children together. Our experience was about acting out a projectural structure with the potential to generate change and characterised by systematic and recursive processes of observation, documentation, evaluation (interpretation) and feedback about the learning experience and the processes implemented therein. In particular, the processes of evaluation and self-evaluation utilised by the team, and deeply connected to the phases of reflection and meaning-building, provided room for the articulation of the strategies employed and for the levels of knowledge progressively acquired by the children. The intent of defining our design approach highlighted the necessity of recognizing the fundamental importance of some underlying structures of the pedagogical project, which constituted the starting point of our reflections: the educational context, the relation between families and educational institutions, the team group (made up of educators, teachers, auxiliary personnel, “atelierista” and pedagogical coordinator). In order to build new competences and new viewpoints, teachers slowly veered towards a different posture: that of a curious researcher who managed to elaborate the itineraries to knowledge and acquire a new awareness generated by common learning spaces thanks to continuous interchange between action and reflection in cooperation with one’s colleagues.

Using Problem-Based Learning to Boost Social Studies Performance: Classroom Action Research in Grade 5 at SD INPRES 3 Talise

The role of education in developing effective problem solvers, critical thinkers, and responsible members of society is of great importance. This research deals with the low performance in social studies subjects caused by the continued application of conventional teaching models. The aim of this study is to improve the learning outcomes of grade V students in social studies subjects at SD INPRES 3 Talise by applying the Problem-Based Learning (PBL) model. This classroom action research was conducted in two cycles, following the Kemmis and McTaggart model, involving 22 students from grade V. Data were collected through tests, observations, and interviews, then analysed quantitatively and qualitatively. Initial observations revealed that only 36.36% of students achieved the learning objectives with an average score of 50.90. The implementation of PBL involved the collaborative planning, action, observation, and reflection phases. The results demonstrated significant improvements in student engagement and learning outcomes. The average score increased, and the percentage of students who achieved the learning objectives rose significantly, respectively from 63.63 in cycle I to 81.59 in cycle II. However, the average score did not yet reach the KKM. Furthermore, the percentage of completeness has also increased, namely in cycle I by 59.09% and cycle II by 86.36%. This research demonstrates that PBL can effectively enhance the quality of social studies education by fostering learning.

Beam-steering by a phase-transition metal-based 1-bit programmable metasurface

Abstract Here the beam-steering mechanism is demonstrated using a 1 bit coded metasurface at 2.5 THz. Each unit cell of the metasurface is loaded with vanadium dioxide (VO2) which undergoes phase transition upon excitation by an external stimulus. The electrical and magnetic properties of VO2 change as the transition takes place from insulator to metal resulting in a reflection phase change of 180°. When the metasurface is excited by a microstrip patch antenna placed at a focal distance above it, the reflected beam is directed at an angle of 22°, as a result of anomalous reflection. By changing the coding pattern of the metasurface, the reflected beam is redirected at −22°. Four different coding patterns have been proposed to depict beam-steering action by the metasurface. The maximum gain registered by the reflect-array integrated antenna is 21 dBi at 2.5 THz. THz beam steering assists in forming directional beams which can be deployed in wireless transmission of THz waves.

Practicality of syntax soft skill-based learning (Ss-BL): a new model in web-based entrepreneurship learning

The soft skills-based learning (Ss-BL) learning the methodology was proposed as an innovative approach to facilitate experiential learning in authentic real-world contexts. This was created to address the shortcomings of the Experiential Learning (EL) approach in enhancing student communication proficiency. Thus, this study's goal is to evaluate the viability of the Ss-BL learning paradigm. In this work, confirmatory factor analysis (CFA) and the Mile and Huberman methodology were employed in an exploratory sequential mixed methods approach. The paradigm for Ss-BL learning is created by conceptualization, theorization, hypothesization, and finalization phases. The research data was acquired via the process of document analysis and conducting a Focus Group Discussion (FGD). A focus group discussion (FGD) was carried out with a sample of 5 experts for research purposes. A non-test was the tool used in the FGD. The Ss-BL model consists of the Motivation, Observation, Real Experience, Implementation, Evaluation, Reflection phases. For all phases, a CFA value of 0.000 was obtained, that is, if the number is less than 2, it means that the Ss-BL model meets the goodness-of-fit model criterion. Among the innovative learning models suggested for entrepreneurial courses in vocational education, the Ss-BL model stands out as both a contribution to the advancement of knowledge and a viable option

Multi-polarized four-mode wideband vortex electromagnetic beams generation through reflective metasurface in Ka-band

Orbital angular momentum (OAM) is a new dimension for improving channel capacity and has been widely studied by scientists. In recent years, there has been an increasing amount of research on antennas and electromagnetic (EM) beams containing OAM, demonstrating its excellent ability in communication. This article proposes a Ka-band multi-mode orbital angular momentum reflectarray antenna (RA) capable of generating four vortex EM beams with four modes (l = −1, 0, +1, +2). The proposed unit cell can cover a 360-degree reflection phase range with a magnitude above 0.88, achieved through a combination of variable-sized and delay-line units. Furthermore, the unit cell’s mirror configuration allows for cross-polarization rejection. Based on these unit cells, a square reflectarray antenna (25 × 25 elements) is designed, fabricated, and measured. The measured results demonstrate that the 1 dB bandwidths for four modes are 25.81% (27–35 GHz, l = −1), 31.25% (27–37 GHz, l = 0), 28.57% (27–36 GHz, l = +1), and 20.69% (26–32 GHz, l = +2), respectively. Notably, the 3 dB gain bandwidths of all modes exceed 40%, with the maximum 3 dB bandwidth reaching 47.62% at mode l = +1. Furthermore, all vortex EM beams of this proposed RA maintain mode purities exceeding 70% within 3 dB bandwidths.