Use Of Beams Research Articles

Flexible terahertz beam manipulation and convolution operations in light-controllable digital coding metasurfaces.

The development of coding metasurface opens an important development direction for beam modulator components. However, the lack of dynamic tunability is a major obstacle to the development and practicality of terahertz coding metasurface. In this work, we design and implement a wireless optically controlled tunable coding metasurface by integrating photosensitive silicon into the metasurface, which realizes the ultra-fast dynamic switching effect of terahertz beam and dynamic convolution operation of 2-bit coding metasurface. We also achieve dynamic modulation of vortex electromagnetic waves based on wireless light-controllable coding metasurfaces. And the genetic algorithm is used to reverse design the array arrangement of the coding metasurface to achieve terahertz broadband radar scattering cross-section reduction. The proposed optically controlled dynamic metasurface developed in this study has the potential to create non-contact metasurfaces, thereby making it a valuable tool for future practical applications.

Dual-wavelength synchronous control method for liquid crystal optical phased array

The liquid crystal optical phased array (LCOPA), as a key beam steering device, has gained increasing significance in the field of space laser communication. With the rapid advancement of space laser communication technology, the demand for precise synchronous control of multi-wavelength beams has significantly increased, particularly in ensuring reliable communication links through synchronized control of signal and beacon beams. The signal beam is primarily utilized for data transmission, while the beacon beam is responsible for path calibration and real-time tracking. However, due to the limitations of natural dispersion effects, conventional LCOPA control methods struggle to achieve synchronized manipulation of beams at different wavelengths, resulting in error accumulation and response delays in communication links, thereby compromising the accuracy and efficiency of information transmission. To address this challenge, this study proposes and validates a dual-wavelength synchronous control method based on LCOPA. The method establishes a phase optimization principle centered on minimizing the least-squares error of complex amplitudes and expands the phase modulation capability of LCOPA hardware, thereby overcoming the natural dispersion governed by the grating equation. Simulation and experimental results demonstrate that this method achieves exceptionally high beam pointing accuracy, meeting the demands of high-precision information transmission in multi-wavelength laser communication. This study provides an innovative technical pathway for the application of LCOPA in multi-wavelength laser communication and establishes a solid theoretical foundation for future experimental research on multi-wavelength control.

Broadband, Single‐Layered, and Optically Transparent Reflective Phase‐Shifting‐Surface Array for Beam Manipulation and Enhanced Wireless Communications

AbstractOptically transparent electromagnetic devices play a crucial role in modern society, yet conventional optically transparent millimeter‐wave devices suffer from high return loss, limited phase shift, narrow bandwidth, high profile, and low optical transparency. Current materials, fabrication processes, and design methodologies restrict the development of high‐performance optically transparent reflective phase‐shifting‐surface arrays or reflectarrays. To address this, a design concept for broadband, single‐layered, and optically transparent reflectarray antennas is reported, which can be integrated with glass windows for beam manipulation and enhanced indoor signal coverage and wireless communications. The proposed reflectarray element employs a single‐layered cyclic olefin copolymer (COC) medium as the dielectric substrate, with fine metal line (FML) patterns under 50 µm width to create multi‐resonant structures for phase range broadening. This architecture combines multi‐resonant phase‐shifting elements with minimal FML structures and low‐loss COC substrate, achieving exceptional antenna performance while ensuring high optical transparency. Wireless communication transmission experiments validate the functionality and performance advantages of the fabricated optically transparent reflectarray. These results substantiate the immense potential and broad application prospects of the novel optically transparent COC dielectric material, the FML structure, and the proposed design concepts and methods in advancing high‐performance optically transparent reflectarrays and related communication systems.

Investigation into Shaped Wide-Beam Reflectarray Surfaces Reflectors as Passive Repeaters in Wireless Networks

This paper investigates the use of a Reflectarray Surface (RAS) to provide a shaped beam for use as a passive repeater in a wireless network. A shaped beam can be desirable as it may provide coverage over a dead-spot region. Examples of a flat-topped and sloping top shaped beams having a nominal beamwidth of 30◦ and a steering angle of 40◦ at 10 GHz are investigated, designed using the particle swarm optimizer in MATLAB. Measurement and simulation from CST show reasonable agreement to the 'array factor' synthesis patterns but display practical detuning effects that may limit this approach. Additionally, it was noted element factor has a more significant impact on such beam shaping.

Dynamic manipulation of ultrasonic beams by coding Moiré metasurfaces

Dynamic acoustic beam manipulation via tunable acoustic metasurfaces (AMs) has attracted significant attention. However, most current tunable AMs are primarily designed for airborne sound, feature complex structural components, and serve a singular purpose. This study proposes a coding Moiré metasurface (CMM) consisting of two cascaded acoustic coding metasurfaces (ACMs) to dynamically manipulate ultrasonic beams in water. The CMM merges the characteristics of Moiré AMs and coding and can achieve different ultrasonic beam manipulations by rotating the ACM and changing the coding sequence. This is demonstrated by presenting CMMs with stripe and checkerboard coding patterns: the former split an ultrasonic beam into two dynamically omnidirectional scanning beams, while the latter divided it into four sections. Finally, two coding bits are employed to construct the CMM samples: a water unit for bit “0” and a photosensitive resin unit for bit “1.” Experimental results demonstrate that the CMM can dynamically manipulate ultrasonic beams. The proposed CMMs hold substantial potential for acoustic communication and dynamic detection applications.

Efficient polarization emission from metasurface-integrated resonant cavity light-emitting diodes

Abstract The pursuit of advanced illumination and display technologies has driven the development of beam manipulation for GaN micro-sized light-emitting diodes (LEDs). To realize an efficient polarization emission light source, we propose metasurface-integrated resonant cavity light-emitting diodes (RCLEDs), incorporating a dual-layer embedded photonic crystal (PhC) within the GaN cavity, and placing a resonant-cavity reflector (RCR) on top of the existing distributed Bragg reflector (denoted as PhC-RCR-RCLED). Numerical simulations reveal a significant enhancement in emission efficiency along with an improved ability to manipulate the emission beams. The averaged transmittance, deflection efficiency, and collection efficiency at the central wavelength for both x- and y-polarizations are 66.9%, 79.6%, and 53.6%, respectively. Compared to the traditional RCLED, our PhC-RCR-RCLED achieves 5.3, 1.2, and 6.3 times enhancements in these three efficiencies. Our scheme paves the way for more efficient and controllable light sources.

Dual-band polarization-controlled metasurface with independent amplitude-phase coding for versatile beam forming.

Digital coding metasurfaces have gained considerable attention for their potential to bridge physical and information sciences. However, existing metasurfaces are often restricted to either phase-only or amplitude-only control and typically operate within a single frequency band or polarization, limiting their functionality in advanced electromagnetic applications. This study proposes a dual-band metasurface with independent amplitude-phase coding for polarization-controlled beam manipulation, addressing these limitations. The designed metasurface features a three-layer structure that integrates resistive films and optimized geometries, allowing simultaneous and independent control of amplitude and phase for linearly polarized (LP) waves in the X-band and circularly polarized (CP) waves in the Ku-band. Through digital coding, it achieves simultaneous 1-bit control over amplitude and phase, facilitating flexible beam steering and complex wavefront manipulation across distinct polarizations and frequencies. A functional prototype was designed, simulated, fabricated, and experimentally tested. The results show close alignment between simulations and experimental measurements, confirming the metasurface's versatile modulation capabilities. This advancement provides a robust platform for applications in wireless communication, radar systems, and adaptive electromagnetic wave engineering, offering significant improvements in design flexibility and operational bandwidth.

Dynamic Control of Airy Beams Using Real-Time Phase-Amplitude Encoding on a Spatial Light Modulator

Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy beams by utilizing computer-generated holograms with phase-amplitude encoding on a phase-only spatial light modulator (SLM). We successfully generated and controlled Airy beams by imposing dynamic phase masks that manipulated both the phase and amplitude of the field, which sets our approach apart from conventional methods with only phase manipulation. By directly encoding in situ such a hologram and transferring it to an SLM, we are able to control the initial position and rotational orientation of Airy beams without relying on mechanical movement or traditional optical setups involving lenses and apertures. Generating Airy beams in any initial position and rotational direction is anticipated to significantly impact applications such as optical trapping, optical communication, and biomedical imaging by providing a flexible platform for dynamic Airy beam manipulation.

Reconfigurable Generation and Spin Manipulation of Structured Beams Based on Cascaded Liquid Crystal Pancharatnam–Berry Phase Elements

Reconfigurable Generation and Spin Manipulation of Structured Beams Based on Cascaded Liquid Crystal Pancharatnam–Berry Phase Elements

Research on terahertz bessel beams based on metasurface

Traditional terahertz imaging systems are constrained by a limited depth of field, which leads to blurry images outside the focal point. To address this limitation, we designed a metasurface with rectangular pillar-structured units based on the transmission phase using a ceramic slurry. Using the finite-difference time-domain method for calculations and simulations, the arranged metasurface unit cells in a ring configuration produced a Bessel beam with a non-diffracting distance of 30 mm. The study found that the phase gradient, light source divergence angle, material refractive index variation, and processing errors influenced the beam propagation characteristics. Notably, the phase gradient and light source divergence angle are directly proportional to the non-diffracting distance and significantly affect the performance of imaging system. The metasurface designed in this study enhances the depth of field of terahertz imaging systems and offers novel insights into the manipulation and application of terahertz beams. This innovation has potential applications in fields such as terahertz imaging and nondestructive testing.

Low-cost spatially variable polarizers via polarization holography.

In this study, we propose a novel, to the best of our knowledge, method for designing low-cost, continuously spatially variable polarizers using polarization holography. We use these devices to generate vector vortex beams and detect scalar vortex beams. Our approach begins with designing polarization holograms that act as polarizers, each with distinct transmission axes recorded at various polar angles on polarization-sensitive materials using a dynamic recording system. This process results in the fabrication of spatially variable polarizers. By adjusting the distribution of these polarization holograms, various types of spatially variable polarizers can be produced. Experimental results confirm the reliability and effectiveness of this method. This work not only advances the understanding of polarization holography but also expands its applications in the manipulation and detection of vortex beams.

POSITRON SOURCES OF THE MULTIFUNCTIONAL ACCELERATOR COMPLEX OF NSC KIPT

The possibility of producing positron beams using an electron recycler, the conceptual design of which is being developed at KIPT, is considered. The positron flux after the tantalum converter was estimated. The efficiency of the process of injection and acceleration of positrons to 181 and 356 MeV for high-energy physics experiments was calculated. The characteristics of the beam for use in structural studies of solid state physics are considered.

Efficient Beam Manipulation With Phase Symmetry Operations on Transmitarrays for Flat-Top Beams

Efficient Beam Manipulation With Phase Symmetry Operations on Transmitarrays for Flat-Top Beams

Polarization insensitive non-interleaved frequency multiplexed dual-band Terahertz coding metasurface for independent control of reflected waves

Independent control of electromagnetic (EM) waves by metasurfaces for multiple tasks are highly desired and is the recent hot topic of research. In this work we contribute a polarization insensitive frequency multiplexed 2-bit coding metasurface to control the Terahertz (THz) waves in the two operating bands independently. In this regard, as a first step a cascaded meta-atom composed of square rings and/or square metallic patches separated by two polyimide substrates is designed and optimized that provides sixteen independent distinct discrete phases in the reflection geometry. These meta-atoms are then distributed with distinct coding sequences in the two-dimensional spatial plane to realize various bi-functional metasurfaces. As a proof of the concept various full structures are designed and simulated to realize a series of bi-functionalities including anomalous reflection/beam shaping, beam shaping/anomalous reflection, beam deflection/Orbital angular momentum (OAM) beam generation with distinct modes and propagating wave to surface wave (PW–SW) conversion/PW beam manipulation in the lower and higher THz bands, respectively. All the simulation results are in excellent agreement with their theoretical equivalents. We envision that the proposed meta-designs have potential applications for the multi-spectral control of EM waves in THz band. The idea can be further extended to design frequency dependent tri-functional and multi-functional THz meta-devices.

Efficient six-dimensional phase space reconstructions from experimental measurements using generative machine learning

Next-generation accelerator concepts, which hinge on the precise shaping of beam distributions, demand equally precise diagnostic methods capable of reconstructing beam distributions within six-dimensional position-momentum spaces. However, the characterization of intricate features within six-dimensional beam distributions using current diagnostic techniques necessitates a substantial number of measurements, using many hours of valuable beam time. Novel phase space reconstruction techniques are needed to reduce the number of measurements required to reconstruct detailed, high-dimensional beam features in order to resolve complex beam phenomena and as a feedback in precision beam shaping applications. In this study, we present a novel approach to reconstructing detailed six-dimensional phase space distributions from experimental measurements using generative machine learning and differentiable beam dynamics simulations. We demonstrate that this approach can be used to resolve six-dimensional phase space distributions from scratch, using basic beam manipulations and as few as 20 two-dimensional measurements of the beam profile. We also demonstrate an application of the reconstruction method in an experimental setting at the Argonne Wakefield Accelerator, where it is able to reconstruct the beam distribution and accurately predict previously unseen measurements 75× faster than previous methods. Published by the American Physical Society 2024

Achieving fine tailoring of elastocaloric properties of laser powder bed-fused NiTi alloy via laser beam manipulation

Laser powder bed fusion (LPBF) technology enables the development of NiTi alloys with complex geometries and tunable phase-transformation temperatures (PTTs). This technology is increasingly acknowledged as promising in the field of elastocaloric (eC) refrigeration. However, the mechanisms governing the manner in which this technology tunes the eC performance remain ambiguous. This study evaluated the fine-tuning of the eC properties by regulating Ni evaporation through laser manipulation. Our results demonstrate that although adjusting Ni loss via laser heat input can effectively control the PTTs, inappropriate combinations of laser parameters may result in lower than anticipated cooling capacity (ΔTad) and coefficient of performance (COPmat) of produced samples. An excessive heat input results in Ni evaporation and in grain coarsening through the remelting and combination of fine grains owing to overlapping molten pools. Lower Ni enhances the phase-transformation enthalpy (ΔHtr). However, larger grains increase the energy dissipation and thereby, counteracting ΔTad improvements. Theoretical analysis and experiments revealed that finer grains increase the misorientation angles. This hinders the dislocation motion and thereby, enhances the mechanical properties. Meanwhile, coarser grains can more conveniently promote PT and thereby, increase ΔHtr. Thus, based on the naturally controllable grain size heterogeneity in LPBF-manufactured NiTi alloys, we propose optimizing the eC properties by controlling the morphology of the molten pool. Thermal-history simulations could balance this relationship. Ultimately, we developed two NiTi alloys for both high-temperature (70 °C) and room-temperature (25 °C) refrigeration. This study has provided effective insights for customizing high-performance eC components such as multistage caloric cascade regenerators, using additive manufacturing.

Full-space metasurfaces for independent manipulation of transmission and reflection.

In recent years, beam manipulation using metasurfaces has evolved from being limited to either a transmission or reflection space to encompassing a full space. However, existing methods still inevitably require complex systems and are unable to achieve continuous and arbitrary phase manipulation. Here, one type of a bilayer metasurface is proposed to simultaneously manipulate reflection and transmission phases continuously and independently, which also makes the optical system more compact without requiring any analyzers and enhances the degree of freedom for full-space beam manipulation. As a proof-of-concept demonstration, one device is designed to show different holograms in transmission and reflection spaces. Additionally, the Dammann grating designed in the reflection hologram increases the information capacity. The proposed method may pave the way toward achieving a variety of applications such as multi-channel beam manipulation and multifunctional optical devices.

Past, present, and future of hybrid plasmonic waveguides for photonics integrated circuits

This article addresses the past, present, and future status of hybrid plasmonic waveguides (HPWs). It presents a comprehensive review of HPW-based photonic integrated circuits (PICs), covering both passive and active devices, as well as potential application of on-chip HPW-based devices. HPW-based integrated circuits (HPWICs) are compatible with complementary metal oxide semiconductor technology, and their matched refractive indices enables the adaptation of existing fabrication processes for silicon-on-insulator designs. HPWs combine plasmonic and photonic waveguide components to provide strong confinement with longer propagation length Lp of HP modes with nominal losses. These HPWs are able to make a trade-off between low loss and longer Lp, which is not possible with independent plasmonic and photonic waveguide components owing to their inability to simultaneously achieve low propagation loss with rapid and effective all-optical functionality. With HPWs, it is possible to overcome challenges such as high Ohmic losses and enhance the functional performance of PICs through the use of multiple discrete components. HPWs have been employed not only to guide transverse magnetic modes but also for optical beam manipulation, wireless optical communication, filtering, computation, sensing of bending, optical signal emission, and splitting. They also have the potential to play a pivotal role in optical communication systems for quantum computing and within data centers. At present, HPW-based PICs are poised to transform wireless chip-to-chip communication, a number of areas of biomedical science, machine learning, and artificial intelligence, as well as enabling the creation of densely integrated circuits and highly compact photonic devices.

Multidimensional Manipulation and Encoding of Versatile Vector Vortex Beams Empowered by Phase-Change Metasurfaces

Multidimensional Manipulation and Encoding of Versatile Vector Vortex Beams Empowered by Phase-Change Metasurfaces

Generation of dual vortices with controlled topological charges based on spin-decoupled moiré metalens.

By their powerful talent in manipulating optical parameters, metasurfaces demonstrate great ability in the generation of the vortex beams. Until now, vortex beam generators constructed by metasurfaces mostly lack tunability, which reduces the scope of their applications. Here, spin-decoupled moiré metalenses composed of two cascaded all-dielectric metasurfaces are designed. Utilizing mathematical derivation and numerical simulation, dual vortices with variable topological charge can be generated under the incidence of orthogonal circularly polarized light by tuning the mutual rotation between the two cascaded metasurfaces. Meanwhile, vector vortex beams can be produced by superposition of dual focused vortices under the linearly polarized light illumination and whose vector polarized states can also be manipulated by mutual rotation. This work provides a flexible design strategy for continuous manipulation of singular beams, which have potential applications in optical communication, microparticle manipulation, and super-resolution imaging.