Beam Steering Research Articles

A dynamic beam switching metasurface based on angular mode-hopping effect

Fast and versatile beam forming and steering technologies are now crucial for various emerging applications, including wireless optical communications and optical switches. However, these technologies often rely on expensive components, such as spatial light modulators (SLMs) and optical phase arrays (OPAs), which come with complex and power-consuming control systems. In response to this challenge, we propose a dynamic beam-switching method inspired by the mode-hopping effect of lasers. As a proof of concept, we introduce the dynamic beam switching metasurface (DBSM) design, featuring an in-plane mechanical actuation system. Our numerical analyses, based on the finite element method (FEM), demonstrate that the proposed DBSM exhibits versatile beam forming and steering functionalities. These include beam splitting and omnidirectional beam steering. Moreover, we anticipate that the tuning speed of the DBSM will reach the kilohertz (kHz) range or even higher when utilizing a microelectromechanical systems (MEMS) actuator, building upon pioneering research in this field. We envision it holds promising applications in areas such as light detection and ranging (LiDAR), optical wireless communication devices, and optical switches.

Reducing beam tracking complexity using a phase ramp and Fresnel lens when steering beams using spatial light modulators.

Steering multiple laser beams using spatial light modulators (SLMs) creates unwanted diffraction and reflections that are not modulated by the SLM, which can make beam tracking difficult. A novel, to the best of our knowledge, and simple beam steering methodology is proposed, which aims at reducing the influence of this clutter while maintaining tracking performance. The beam(s) are deliberately defocused before steering with a superposition of a phase ramp and Fresnel lens (PRFL) phase screen on the SLM. As a result, the non-modulated reflections and diffracted light are decreased in relative intensity to the steered beam, in turn allowing simple and standard peak intensity and center of gravity (CG) algorithms for tracking. Hardware demonstration shows tracking performance using the PRFL remained on-par with more complex filtering approaches while adding no additional hardware. This method has potential to improve the communication performance of multi-beam laser communication terminals.

Programmable metasurfaces with high angular stability for arbitrarily-polarized obliquely-incident waves

Programmable metasurfaces show enormous potential in real-time electromagnetic (EM) manipulation and their stable responses to variable EM waves including incident angle and polarization changes are crucial for related applications. However, the demonstrated programmable metasurfaces are commonly considered in normal-incident waves with fixed polarization; how to achieve stable performance in more realistic scenarios of wide-angle and full-polarized wave incidences is still a challenge. Here, we propose and realize a wide-angle and full-polarization programmable metasurface, which can generate stabilized amplitude and phase responses at both transverse electric (TE) and transverse magnetic (TM) oblique incidences. These are achieved by introducing metallic walls around the metasurface element to reduce element coupling, which greatly improves the angular stability of its reflection responses. The mechanisms of angular insensitivity are analyzed comprehensively, and as a proof of concept, obliquely-incident beam steering, large-angle beam scanning and oblique vortex beam emitting are demonstrated on this programmable metasurface. Both the simulation and experimental results demonstrate that the programmable metasurface can operate well at both TE and TM wide-angle oblique incidences in the upper half space. Our work offers an actual route for improving the angular stability and polarization insensitivity of metasurfaces, which could push them one step closer towards more complicated applications.

Far-field pattern accuracy improvement in planar near-field measurement using infinitesimal dipole modeling

This paper discusses the challenges in accurately measuring the far-field performance of array antennas, which have become more complex and larger due to recent trends in increasing the number of elements and the antenna size. The far-field measurement method, which is a general method for measuring a radiation pattern in a far-field, is difficult to be utilized at a high frequency due to limitations in physical chamber size and difficulty in diagnosing an antenna. In order to improve these problems, a near-field measurement method is used as an alternative. Even though using a near-field measurement, the accuracy of the derived far-field pattern is reduced at low elevation angles due to zero-padding of data outside the measurement area. The integration of the near-field measurement with the source reconstruction is a promising approach to enhance the measurement limits of the far-field pattern analysis. This paper aims to extend the previous work to accurately predict the far-field radiation pattern, especially in the low elevation angles. The verification of the proposed method is performed for a standard gain horn and 4 by 4 patch array antennas, with and without beam steering.

Compact fully metallic multi‐mode waveguide antenna for cellular communications

AbstractThe needed isolation between elements for high‐performance beam steering array antennas is a challenging task especially when the distance between the antenna elements is reduced. To tackle this problem, the authors report a multi‐port multi‐mode single‐antenna with beam steering capability (±7 deg) suitable for cellular communications. The multi‐port multi‐mode characteristic of the proposed antenna enables size reduction and better taper efficiency than antenna arrays operating in the 3.3–3.7 GHz cellular band. The reported antenna exploits four Transverse Electric modes to modify the half‐power beamwidth of the radiation from 20° to 41° as required in cellular communication.

Secured THz communication in photonic microcell networks based on spatial wave mixing of steered beams

Future 6G communication systems are envisioned to expand their carrier frequency to the THz region, where a broad unexplored region of spectrum is available. With this expansion, THz wireless communication has the potential to achieve ultra-high data transmission rates of up to 100Gbit/s. However, as large amounts of data are transmitted in an open wireless environment, there are significant concerns regarding communication security due to the susceptibility to eavesdropping, interception, and jamming. In this work, we proposed a secure approach for THz wireless communication based on spatial wave mixing and flexible beam steering. To achieve this, two frequency-modulated THz waves, which are generated by photonic THz sources and carry encrypted information with true randomness, are mixed at a THz envelope detector with an exclusive-OR logic operation. We analyzed the possible spatial location for the THz detector to ensure a secure microcell network deployment. Our results demonstrate that the size of the decryptable region is directly dependent on the directivity and width of the emitted THz beam. To address this, we have developed an array antenna with integrated uni-traveling-carrier photodiodes (UTC-PDs), which is capable of generating THz waves while also improving the flexibility of beam pointing, allowing for greater control over the location and size of the decodable region. By controlling fiber-optic delay lines, we successfully demonstrated that the directional gain of a 200GHz wave is increased by 8dB through a 1 × 3 UTC-PD-integrated planar bowtie antenna (PBA) array, together with continuous beam steering from -20° to 10°. Additionally, using a 1 × 4 UTC-PD-integrated PBA array to emulate two encryption transmitters and a Femi-level managed barrier diode to detect spatially mixed THz waves, we successfully achieved a feasibility experiment for real-time 200Mbit/s location-based decryption in the 200GHz band. These results indicate that the proposed scheme is feasible for secured THz communication, and would be a powerful candidate to mitigate security risks in 6G microcell networks.

Low-loss vanadium dioxide-enabled mmWave tunable reflective electromagnetic surface with complementary unit cells for wave manipulation

This study presents a novel implementation of vanadium dioxide (VO2) phase change material in an electromagnetic (EM) surface with beam steering capabilities. For the first time, we present the design, fabrication, and measurement of a globally actuated, VO2-based beamforming reflective EM surface. We propose a design featuring complementary unit cells that enable beam steering with a single excitation, marking a pioneering use of low-loss VO2 in creating a complementary EM surface for the mmWave band. The unit cells incorporating VO2 exhibit low-loss characteristics, with −0.92 and −1.9 dB in the hot state and −0.49 and −0.25 dB in the cold state, respectively. We incorporate both positive and negative phase variants alongside two temperature-independent phase unit cells. The complementary design enables us to utilize two beam operating states, effectively exploiting the otherwise unused cold state. We experimentally demonstrated beamforming at ±5° and ±10° from the broadside. In the case of ±10°, the measured gains at 35 GHz in the cold and hot states were 19.4 and 20.3 dB, respectively, which aligned well with the simulated gains of 20.9 and 21.5 dB. Manipulation of the electromagnetic wave direction with a single excitation has the potential for imaging, sensing, and communication applications. The complementary unit cell design methodology can be further adapted for mmWave beamforming, absorbing, and cloaking reconfigurable EM surfaces. Furthermore, the use of VO2 can be extended up to sub-THz frequencies due to the wideband, low-loss characteristics compared with conventional reconfigurable devices, such as PIN diodes or MEMS switches.

The Curriculum in NDT Training Have to Include Basics Information Technology to Accomplish Reliability of Automated NDT Result's

Automation in Non-Destructive Testing (NDT) is a reality of modern manufacturing and quality assurance. Information technology applications are simultaneously developed and applied to different fields of NDT methods. The future of doing reliability checks using automated system is inevitable. The results are important to make a variety of decisions regarding the quality of a product and/or service, hence affecting safety and reliability. Depending on artificial intelligence and quantum device development, various NDT training schemes have to adopt a new curriculum to address the issue of the basic knowledge of information technology and automation in NDT. NDT operators are basically dependent on the end results of software, in which the software developer uses a set of algorithms. These are obtained in three categories; 1) Real time database; 2) Synthetic database and 3) Hybrid or combination of them. The developers should know how the NDT systems run and NDT operators in the other hand know the mechanism of the program, so that appropriate action can be taken, in case there is a missed detection, or a detected indication is not very much detrimental to the reliability of the part (Over sizing or wrongly evaluated). For example, a set of algorithms are used to create the focal laws in a phased array ultrasonic test software in space of 1˚ beam steering. Each has a limit of maximum up to 2nd Critical angle. Operators try to copy the same algorithm and set up to 89˚ refraction angle, which will just create creep wave with unreliable results to detect effective size the reflector. Programming knowledge of the operator can effectively eliminate this type of unreliability. In various Schemes of NDT Syllabus which are in common place to employ and train plus certify operators does not have it; actually, the operators do the scope of work which does includes application of Artificial Intelligence (AI) and Software. With the development of Q coupler (Quantum Computing) system, it is obvious to adopt the upcoming technology into the application of NDT industry. Training needs to update the curriculum accordingly. The current topic has intended to focus on the training gap and to address related kind of unreliability.

Beam Steering Toward Multibeam Radiation by Time-Coding Metasurface Antennas

Beam Steering Toward Multibeam Radiation by Time-Coding Metasurface Antennas

Dynamic Transition from Branched Flow of Light to Beam Steering in Disordered Nematic Liquid Crystal

AbstractOrientational ordered soft matter possessing diverse microstructures has become a focal point of scientific research and technological exploration, thanks to its advancements in serving as an indispensable optical platform enabling propagation of light with multidimensional and manipulatable states. Herein, a facile way is developed to manipulate the in‐plane light beam transition dynamics by harnessing a time‐variable nematic liquid crystal (NLC) film through the electrical‐field‐induced topological defects. The results show that the dynamic change of optical branched flow is associated with the growth in the correlation length of optical potential and the reduction in the density of topological defects. The optical branching can continuously transform to deterministic and tunable beam steering at the low‐defect‐density regime through annihilation kinetics of defects. The explored soft matter system provides an excellent planar platform for the fundamental physics of light interacting with topological defects and may offer new perspectives for novel optics elements toward the applications of soft matter photonics.

Antenna Systems for Satellite Communication Terminals

This Roadmap presents the research trends on antenna systems for Satellite Communication terminals. To address the challenges posed by this application in terms of wide fractional bandwidth and large field-of-view, several antenna concepts and architectures are being investigated, which can be grouped in three main technology areas: fully electronic scan, fully mechanical scan with unconventional steering mechanisms and beam switching. Design techniques, current results and future developments are outlined, considering representative examples for each technology area.

Design of a Fourier-transform spectrometer for detector characterization on CMB polarization telescope

We present the design of a Fourier-transform spectrometer (FTS) tailored for operation within the frequency range of 75 GHz to 300 GHz, offering a spectral resolution surpassing 2 GHz. This FTS can be used for characterizing detectors on a Cosmic Microwave Background (CMB) Polarization Telescope for the observation of CMB B-mode polarization. The FTS instrument is divided into the primary part, housing a Martin-Puplett interferometer (MPI) module, and the coupled part, which incorporates a beam expanding module and a beam steering module. An in-depth performance analysis focusing on the MPI module, involving considerations such as the orientation of the beam splitter, dihedral angle of the roof-top mirrors, and positioning uncertainty of the scanning mirror, has been conducted by using a simulation tool. Results indicate that the spectral characteristic remains unaffected by variations in the Reflection/Transmission ratio of the beam splitter, with any deviation from the 1:1 ratio uniformly decreasing intensity. The impact of dihedral angle errors of roof-top mirrors (below 0.02 degrees) and positioning uncertainty in the scanning mirror (lower than 3 × 10-3 mm) on the system performance is acceptable for the design of the FTS. The beam expanding module is capable of enlarging the output beam of the MPI module to roughly a 150 mm-radius. The beam steering module allows for directional adjustments within the range of +17 degrees to -17 degrees relative to the normal of the target plane. Preliminary testing on the MPI prototype reveals a spectral resolution of 1.5 GHz for the measured frequency.

Comparison between PA and PWI/TFM Techniques for Non-Destructive Testing of Carbon Steel Weld

The Total Focusing Method (TFM) technique is an advanced Non-Destructive Testing (NDT) Ultrasonic Testing (UT) technique well known for its representative images of high resolution. It was firstly developed together with Full Matrix Capture (FMC) acquisition which can be substituted later by Plane Wave Imaging (PWI) acquisition for its improved acquisition speed and gain reserve without lowering the image quality. For these advantages, the PWI/TFM technique is tending to be more and more widely implemented. This article presents some results of the related study on PWI/TFM technique. Starting by PWI/TFM reconstruction principles, mainly on the influences of beam steering settings and corresponding inspection coverage in predefined Region of Interest (ROI), it focuses on the comparison on the indication amplitudes of planar discontinuities between classical Phased Array (PA) technique and PWI/TFM technique.

Compact unidirectional waveguide grating emitter with enhanced wavelength sensitivity based on the hybrid plasmonic mode

Waveguide grating antennas are widely adopted in beam-steering devices, typically enabling the beam steering in longitudinal direction within a two-dimensional scanning optical array by changing the input wavelength. However, traditional waveguide grating antennas suffer from limited tuning range due to low dispersion of the gratings. In this paper, a compact silicon grating waveguide antenna array is proposed with enhanced wavelength sensitivity by introducing a periodically modulated hybrid plasmonic mode. The hybrid plasmonic mode is supported by the hybrid plasmonic waveguides (HPWs) composed of silicon waveguides and periodic subwavelength silver strips. In order to convert the guided waves to the radiated waves, a series of silicon emitting segments are deposited above the HPWs. Additionally, the horizontally arranged array of HPWs also acts as a reflector of the downward radiation, resulting in an effective unidirectional emission. Through the optimization of physical parameters, the proposed antenna array achieves a wavelength-length tuning efficiency up to 0.3°/nm within the wavelength range of 1500∼1600 nm, exhibiting a significant improvement compared with traditional ones. Moreover, an average upward emissivity exceeding 80% with a maximum value of 89% within the 100 nm bandwidth is demonstrated through the numerical simulations. The proposed compact antenna array provides an alternative solution in realizing large-scale integrated high-tuning-efficiency optical beam-steering devices.

Disturbance Observer-Based Anti-Shock Controller for Laser Beam Steering Systems

Disturbance Observer-Based Anti-Shock Controller for Laser Beam Steering Systems

Enhancing the field-of-view of spectral-scanning FMCW LiDAR by multipass configuration with an echelle grating.

We present a spectral-scanning frequency-modulated continuous wave (FMCW) 3D imaging system capable of producing high-resolution depth maps with an extended field of view (FOV). By employing a multipass configuration with an echelle grating, the system achieves an FOV of 5.5° along the grating axis. The resulting depth maps have a resolution of 70 × 40 pixels, with a depth resolution of 5.1 mm. The system employs an echelle grating for beam steering and leverages the multipass configuration for angular FOV magnification. Quantitative depth measurements and 3D imaging results of a static 3D-printed depth variation target are demonstrated. The proposed approach offers a promising solution for enhancing the FOV of spectral-scanning FMCW LiDAR systems within a limited wavelength-swept range, thereby reducing system complexity and cost, paving the way for improved 3D imaging applications.

Dielectric elastomer-driven liquid prism enabling two-dimensional beam control

In this paper, a dielectric elastomer (DE)-driven liquid prism enabling two-dimensional beam control is proposed. The proposed liquid prism consists of a flexible driver and a liquid cavity. The glass plate is driven by DE to change the tilt angle of the liquid-solid interface for beam steering and field of view (FOV) tuning. The maximum optical deflection angle of 8.13° and response time of 76.77 ms were measured, the variable FOV capability was also verified. The proposed liquid prism can be used in beam modulation, microscope systems.

Rotating twisted templates for imprinting polarization gratings with a sub- to dozen-micron period.

In this Letter, we report and experimentally demonstrate what is to our knowledge a novel scheme for imprinting polarization gratings (PGs) with a pair of templates. Compared with the traditional method that a single template can only imprint PG with a single period, cascading two templates can control the period of imprinted PG at will. However, the low diffraction efficiency is inevitably caused by cascading two templates. Therefore, a rigorous coupled wave analysis (RCWA) is adopted to design a multi-twisted template to address this challenge. As a proof of concept, two multi-twisted templates with a period of 1.6 μm were fabricated, and PGs with a large period range from 0.4 to 48.6 μm were successfully imprinted. The proposed scheme is expected to enable rapid, robust, and high-quality mass production of beam steering, large-angle deflectors, and diffractive optical couplers.

Miura Origami‐Inspired Reconfigurable Phase Gradient Metasurface for Linearly and Circularly Polarized Differential Modulation

Miura origami's reconfigurable characteristic and structural asymmetry, combined with electromagnetic (EM) wave manipulation, crashed a unique spark. However, the complexity of the three‐dimensional (3D) origami structure after folding makes it challenging to study the phase regulation mechanism. Here, we propose a reconfigurable phase gradient metasurface based on Miura origami and derive the underlying mechanism of phase modulation in detail under linearly and circularly polarized (LP and CP) incidence. We adopt the one‐dimensional (1D) gradient design along the x direction to verify the idea. The phase calculation formulas are given under LP and CP incidence through the Jones matrix's derivation. The beam deflector angles corresponding to LP and CP waves are identical in the planar state. As the folding angle increases, the phase evolution rules corresponding to the LP and CP waves are discrepant, leading to differential beam steering. Finally, the origami sample is processed for verification, and the experimental data are consistent with the simulation and theoretically calculated values. We believe this work can help analyze the EM behavior of complex 3D origami structures and lay a foundation for designing a multifunctional EM origami metasurface.

Multi-function digital THz-metasurfaces based on phase change materials

An effective and digitally tunable reflective multi-function metasurface in the THz band is proposed. The introduced planar structure consists of an array of a well-designed double-split SRR (DSSRR) utilizing phase-change materials (PCMs) in the gap regions, leading to the controllable function of the metasurface due to the tuning of the crystallization level of PCMs. According to Pancharatnam-Berry's principle, this effect creates different electromagnetic responses only by employing two types of unit cells (bit-0 and bit-1) based on the proper addressing of the PCMs in the structure. It is reported that by digitally changing the coding sequence of the metasurface, it is individually capable of performing different functions such as polarization rotation, beam steering, and RCS reduction. The computational results have been verified by appropriate analytical equivalent electric-circuit modeling and the theory of antenna-arrays. The studied planar-structure with its tunable and coding properties might be suggested for advanced applications in THz sensing, communications, and imaging systems.