Beam Steering Technology Research Articles

Scattering-Free and Fast Response Polymer Brush-Stabilized Liquid Crystals Beam Steering Using Surface-Initiated Polymerization Technique.

Nonmechanical fast response optical beam steering technology is increasingly essential for telecommunications, imaging systems, optical sensing, displays, and military applications. Polymer network liquid crystal (PNLC) beam steering can achieve submillisecond response times but faces limitations due to scattering issues arising from the refractive index mismatch between the polymer network and the liquid crystals (LCs). In this article, we demonstrate a scattering-free, fast-response LC beam steering by using polymer brushes to stabilize the gradient refractive index. First, the initiator is incorporated into the alignment layer and the monomer is mixed into the LC layer. Surface-initiated polymerization (SIP) is then employed to grow the polymer brushes exclusively on the substrate's surface, thus confining the polymer network's growth to the LC bulk and reducing interfacial scattering. For polymer brush stabilized liquid crystal (PBSLC) beam steering device with a period size of 225 μm and a cell gap of 7.2 μm, the average transmission rate reaches 88% in the visible light spectrum with a haze value of only 6.91. The steering angle is 0.16, and the diffraction efficiency is 80.3%. When a voltage of 35 Vrms is applied, the primary energy can be tuned to the zeroth order, with a response time close to 1 ms. By cascading two PBSLC beam steering devices with opposite steering directions, the primary energy of the beam can be adjusted between zeroth, +1, and -1 order. This method requires only a UV light source, a precision displacement stage, a power supply, and a mask, avoiding the need for expensive equipment and complex electrode fabrication. By adjustment of the phase change period, step width, and number of steps during fabrication, the steering angles and diffraction efficiency of the PBSLC beam steering device can be easily controlled, highlighting its significant potential for industrial production.

Performance and compensation method of first-order liquid crystal beam-steering system under continuous wave laser irradiation

The effects of laser irradiation thermal deposition on the performance degradation of liquid crystal (LC) devices in high-power laser systems are extremely vital. In this study, the first-order beam-steering system (FBS) was developed using a passive liquid crystal polarization grating (LCPG) and liquid crystal adjustable wave-plate (LCAW). The LCPG was prepared by holographic exposure technology, and the LCAW was prepared using the standard LC cell preparation process. We investigated the influences of diffraction efficiency of FBS under a 1070-nm continuous-wave (CW) laser irradiation. The energy is concentrated in the −1st order at first. When the half-wave retardation was reached, all the energy is concentrated in the +1st order (∼97 %), and the beam is deflected. Once the phase retardation decreases below the half-wave retardation, the energy gradually reconcentrates in the −1st order. When the LCAW fails, the diffraction the energy is refocused to the −1st order by the LCPG. The results indicated that both thermal deposition and driving voltage reduce the phase retardation of the LCAW, generating a variation of energy between in ±1st orders. By reducing the driving voltage, this half-wave retardation can be recovered under a certain half-wave voltage and laser power density, and the diffraction efficiency of the +1st order can be compensated to ∼97 %. If the reduced phase retardation is not less than half-wave, the FBS can still be modulated in high-power continuous lasers. Our research provides a reference for the development of beam-steering technology based on LC materials in high-power laser systems.

Beam Steering Technology of Optical Phased Array Based on Silicon Photonic Integrated Chip.

Light detection and ranging (LiDAR) is widely used in scenarios such as autonomous driving, imaging, remote sensing surveying, and space communication due to its advantages of high ranging accuracy and large scanning angle. Optical phased array (OPA) has been studied as an important solution for achieving all-solid-state scanning. In this work, the recent research progress in improving the beam steering performance of the OPA based on silicon photonic integrated chips was reviewed. An optimization scheme for aperiodic OPA is proposed.

Enhancing vehicle/airborne displays with beam steering technology for improved viewing angles

ABSTRACT For vehicles or airborne displays, the limited space and arrangement of operating devices in the cockpit often result in drivers having a certain off-axis viewing angle with the display. This leads to a noticeable degradation in performance parameters such as brightness and colour shift compared to the vertical viewing angle. A beam steering technology applicable to the display field is presented, which simultaneously improves the performance of vehicle/airborne displays in both the large and off-axis viewing angles. When the usage scenario changes, such as acceleration, deceleration, turning, the proposed technology allows for the flexible switching of display modes, effectively aligning the high-brightness and low colour shift high-quality display to the corresponding viewing angle. The simulation results show that the viewing angle performance of displays are effectively improved, which demonstrates that the proposed technology has a promising application prospect to substantially enhance viewers’ visual experience.

A two‐dimensional beam steering Fabry–Pérot antenna employing a liquid‐based reconfigurable metasurface

AbstractA novel 2‐D beam steering technology using a Fabry–Pérot antenna with a liquid‐based reconfigurable metasurface is presented. The antenna employs a reconfigurable partially reflecting surface to regulate phase distribution and adopts a microstrip antenna as feed to realise 2‐D beam steering. The antenna beam can be tilted in four different directions by injecting liquid metal into the specific area of the microfluidic channels embedded in the metasurface. Moreover, the antenna has a simple and compact structure with a low profile. A prototype is manufactured, and good agreement between simulated and experimental results verifies the correctness of the design. The measured results of the manufactured antenna prototype demonstrate that the main beam tilts to maximum values of ±15° and ±28° in the yoz and xoz planes, respectively, between 9.5 and 9.7 GHz.

Micro-fabricated Si subwavelength grating for frequency-domain THz beam steering covering the 0.3-0.5 THz frequency band.

We designed and fabricated beam steering subwavelength grating (BS-SWG) with high efficiency, wide angles, and broadband beam steering in the terahertz (THz) range. Beam steering technology in the THz range by a fixed structure and frequency sweep has to date lacked a device combining high efficiency and a wide beam steering angle. A subwavelength structure using float zone Si, a low-loss dielectric, could combine both of these aspects, but no experimental demonstration in the THz range has been performed to our knowledge. The BS-SWG was designed with an efficiency of 0.708 at 0.4 THz and beam steering angles of -72.1°--34.8° by sweeping the incident frequency from 0.3 THz to 0.5 THz including the Beyond 5 G/6 G communication bands. An efficiency of 0.354 at 0.400 THz and beam steering angles of -74°--34° were experimentally achieved, demonstrating the potential of high-efficiency, wide-angle beam steering for THz communications, imaging, and radar applications.

Photonic integrated multicast switch-based optical wireless data center network

Optical wireless data center networks (OW-DCNs), which employ optical wireless technology and optical wired switching technology, are gaining interest as they promise to eliminate cable complexity, as well as to create high bandwidth interconnections and a low-cost and power-efficient system. In particular, the incorporation of optical tunable transmitters (T-TXs) and passive optical beam steering technologies is a promising way to build an OW-DCN benefitting from the potential of fast optical switching speed, low switch control complexity, and easy reconfiguration. However, the practical deployment of such an OW-DCN remains a challenge as fast (nanosecond) T-TX is required for fast optical switching operation. Implementation of fast T-TX can be realized by an array of lasers and optical gates, which are combined with photonic integration technology to achieve a compact, stable, and efficient nanosecond T-TX. In this paper, we propose an OW-DCN based on arrayed waveguide grating routers and fast T-TXs that exploit photonic integrated circuit multicast switches (PIC-MCSs). This PIC-MCS chip not only offers nanosecond-scale fast optical switching but also plays an essential role in enabling multicast operation, T-TX sharing, and dynamic bandwidth allocation between the intra- and inter-cluster networks. A 4×2 PIC-MCS has been designed, fabricated, and characterized in this proposed OW-DCN system. Experimental results validate that the proposed OW-DCN supports lossless, nanosecond, and multicast switching operation. Moreover, the dynamic bandwidth allocation and optical packet switching capability have been experimentally demonstrated. Finally, system performance with this fabricated PIC-MCS chip in a 4×4 rack OW-DCN is experimentally validated for different transmission scenarios and modulation formats. Wavelength division multiplexing multicast transmission with 50 Gb/s non-return-to-zero on–off-keying signals has been verified with less than 1.5 dB power penalty. 58 Gb/s four-level pulse-amplitude modulation transmission has also shown operation below the forward error correction threshold of 3.84×10−3 for all the different transmission scenarios.

Chaotic microcomb inertia-free parallel ranging

The increasing demand for high pixel acquisition rates in the fields of augmented reality, autonomous driving, and robotics has led to a growing interest in solid-state beam scanning solutions that do not rely on moving parts. As a result, modern photonics has been driving the development of passive beam steering technology to meet these demands. Recently demonstrated imagers based on focal plane arrays, nanophotonic metasurfaces, and optical phased arrays have enabled unprecedented pixel resolutions and measurement speeds. However, the parallelization of >100 lasers and detectors, which has been successfully implemented in commercial time-of-flight sensors, has not been widely adopted for passive scanning approaches. In this work, we demonstrate both inertia-free and parallel light detection and ranging (LiDAR) with microresonator frequency combs. We use 40 independent channels of a continuously scanned microresonator frequency comb operated in the chaotic regime in combination with optical dispersive elements to perform random modulation LiDAR with 2D passive beam steering.

Dynamic Beam Steering and Focusing Graphene Metasurface Mirror Based on Fermi Energy Control

Beam steering technology is crucial for radio frequency and infrared telecommunication signal processing. Microelectromechanical systems (MEMS) are typically used for beam steering in infrared optics-based fields but have slow operational speeds. An alternative solution is to use tunable metasurfaces. Since graphene has gate-tunable optical properties, it is widely used in electrically tunable optical devices due to ultrathin physical thickness. We propose a tunable metasurface structure using graphene in a metal gap structure that can exhibit a fast-operating speed through bias control. The proposed structure can change beam steering and can focus immediately by controlling the Fermi energy distribution on the metasurface, thus overcoming the limitations of MEMS. The operation is numerically demonstrated through finite element method simulations.

Smart Gateway for Healthcare Networks Based on Beam Steering Technology

To ensure high-reliability communication in healthcare networks, this paper presents a smart gateway system that includes an angle-of-arrival (AOA) estimation and a beam steering function for a small circular antenna array. To form a beam toward healthcare sensors, the proposed antenna estimates the direction of the sensors utilizing the radio-frequency-based interferometric monopulse technique. The fabricated antenna was assessed based on the measurements of complex directivity and the over-the-air (OTA) testing in Rice propagation environments using a two-dimensional fading emulator. The measurement results reveal that the accuracy of the AOA estimation agrees well with that of the analytical data obtained through the Monte Carlo simulation. This antenna is embedded with a beam steering function employing phased array technology, which can form a beam spaced at 45° intervals. The ability of full-azimuth beam steering with regard to the proposed antenna was evaluated by beam propagation experiments using a human phantom in an indoor environment. The received signal of the proposed antenna with beam steering increases more than that of a conventional dipole antenna, confirming that the developed antenna has great potential of achieving high-reliability communication in a healthcare network.

Spatial coupling efficiency of collimators based on gradient-index lens with an angle polish

As high coupling efficiency and return loss are crucial in fiber-optic transmission systems, they have attracted widespread attention. This study proposes a ray-transfer matrix-based mathematical analysis method and experimentally demonstrates a collimator based on a gradient-index lens with an angle polish. The propagation characteristics and coupling mechanisms of the collimators are introduced. A beam-steering technology based on a wedge prism and flat glass is proposed to improve the coupling efficiency of the Gaussian beam using collimators. The proposed method is validated via simulation and experiment. The results are significant in free-space optical communication, optical signal processing, and optical fiber connectors.

On-chip integration of metasurface-doublet for optical phased array with enhanced beam steering

Abstract Optical phased array (OPA), as a promising beam steering technology, however, usually suffers from a narrow field of view (FOV) that limits its performances in applications. A miniaturized compact strategy to enlarge the beam steering angle is quite desirable for the solid-state OPA technique. Here an on-chip metasurface-doublet is proposed to offer angle magnification integrated with a port-selected optical phased array. It is implemented by combing convex and concave metalenses with the quadratic phase distribution, which is precisely integrated on the OPA chip by layer-by-layer fabrication process. Here, the OPA is fabricated in Lithium Niobate on Insulator (LNOI) platform. Our experiments show that the metasurface-doublet is able to achieve 1.54 times FOV amplification in a horizontal direction and with >41% working efficiency. Our results provide a feasible approach to achieve enlarged FOV for wide-angle beam steering and also imply a powerful platform in developing integrated multilayer metasurface devices.

Four-access, 80 mm aperture all phase-controlled liquid crystal laser antenna

High speed, wide range, and high precise beam steering technology are fundamental to free-space optical communication (FSO). Liquid crystal optical phased array (LC-OPA) is capable of achieving non-mechanical beam steering. This paper demonstrates a parallel, four-communication access beam deflection antenna based on LC-OPA, providing a large aperture, wide steering range, and high pointing precision. This antenna is composed of a coarse tracking subsystem using cascaded liquid crystal polarized grating (LCPG) and a fine tracking subsystem based on LC-OPA. The optical aperture is 80 mm × 80 mm, arranged in 2 × 2 subapertures, each serving a single wavelength beam. Besides, a cascaded control platform based on field programmable gate array is proposed to realize low-latency response. This optical antenna achieves a steering resolution of 20 μrad and covers a range of ±12 deg in two dimensions, laying the foundation for simultaneous access of multiple terminals in FSO communication network.

Free-Space Applications of Silicon Photonics: A Review.

Silicon photonics has recently expanded its applications to delivering free-space emissions for detecting or manipulating external objects. The most notable example is the silicon optical phased array, which can steer a free-space beam to achieve a chip-scale solid-state LiDAR. Other examples include free-space optical communication, quantum photonics, imaging systems, and optogenetic probes. In contrast to the conventional optical system consisting of bulk optics, silicon photonics miniaturizes an optical system into a photonic chip with many functional waveguiding components. By leveraging the mature and monolithic CMOS process, silicon photonics enables high-volume production, scalability, reconfigurability, and parallelism. In this paper, we review the recent advances in beam steering technologies based on silicon photonics, including optical phased arrays, focal plane arrays, and dispersive grating diffraction. Various beam-shaping technologies for generating collimated, focused, Bessel, and vortex beams are also discussed. We conclude with an outlook of the promises and challenges for the free-space applications of silicon photonics.

Monolithic coherent LABS lidar based on an integrated transceiver array.

We demonstrate a monolithic frequency-modulated continuous-wave (FMCW) lidar chip with an integrated transceiver array based on lens-assisted beam steering (LABS) technology. It enables beam emitting, steering, receiving, and coherent detecting on a single chip with simultaneous distance and velocity detection. An integrated transceiver is designed with a composite structure of a Bragg grating in the middle and a U-shaped photodetector (PD) surrounding it. For a proof-of-concept demonstration, a chip with 2 × 2 switchable transceiver array is fabricated. A monolithic coherent LABS lidar system with a scanning angle of 2.86° and a scanning speed of 5.3 µs is implemented for 5 m ranging and 0.45 m/s velocity detection.

Accurate optimization technique for phase-gradient metasurfaces used in compact near-field meta-steering systems

Near-Field Meta-Steering (NFMS) is a constantly evolving and progressively emerging novel antenna beam-steering technology that involves an elegant assembly of a base antenna and a pair of Phase-Gradient Metasurfaces (PGMs) placed in the near-field region of the antenna aperture. The upper PGM in an NFMS system receives an oblique incidence from the lower PGM at all times, a fact that is ignored in the traditional design process of upper metasurfaces. This work proposes an accurate optimization method for metasurfaces in NFMS systems to reduce signal leakage by suppressing the grating lobes and side lobes that are innate artifacts of beam-steering. We detail the design and optimization approach for both upper and lower metasurface. Compared to the conventionally optimized compact 2D steering system, the proposed system exhibits higher directivity and lower side-lobe and grating lobe levels within the entire scanning range. The broadside directivity is 1.4 dB higher, and the side-lobe level is 4 dB lower in comparison. The beam-steering patterns for the proposed 2D compact design are experimentally validated, and the measured and predicted results are in excellent concurrence. The versatile compatibility of truncated PGMs with a low gain antenna makes it a compelling technology for wireless backhaul mesh networks and future antenna hardware.

Integrated optical phased arrays with circular architecture on a silicon platform

Optical phased arrays (OPAs) are now at the forefront of photonic research as a key beam steering technology for myriad of photonic applications, including in light detection and ranging (LIDAR), communications, and metrology, among others. Integrated OPAs with narrow beam widths and wide-angle steering are in critical need, especially for LIDARs in autonomous vehicle, drone and airplane navigation, or satellites. In this work, we numerically study the performances of OPAs having a circular layout arrangement. Compared to recently available solutions with 1D linear or 2D rectangular arrays, the proposed circular OPAs are poised to deliver effective suppression of the grating sidelobes, while improving beam steering range and obtaining narrower beamwidths. We demonstrate 110-element circular arrays with sidelobe suppression better than 10 dB and an angular beamwidth of 0.5°. Under a monochromatic operation at a 1550 nm wavelength, such array provides a solid angle steering range of 0.21π-sr, with a perspective for performance improvement by using large number of OPA elements and operating under broader spectral range.

Blind zone-suppressed hybrid beam steering for solid-state Lidar

We demonstrate a blind zone-suppressed and flash-emitting solid-state Lidar based on lens-assisted beam-steering technology. As a proof-of-concept demonstration, with the design of a subwavelength-gap 1D long-emitter array and multiwavelength flash beam emitting, the device was measured to have 5% blind zone suppression, 0.06°/point-deflection step, and 4.2 μs scanning speed. In time-of-flight ranging experiments, Lidar systems have a field of view of11.3°×8.1°(normal device) or0.9°×8.1°(blind-zone suppressed device), far-field number of resolved points of 192, and a detection distance of 10 m. This work demonstrates the possibility that a new integrated beam-steering technology can be implemented in a Lidar without sacrificing other performance.

Spectral imaging of flexible terahertz coding metasurface

Coding metasurfaces have emerged as a promising venue for terahertz (THz) beam steering and beamforming. In this study, we designed a transmission metasurface with a complementary structure based on Babinet's principle. The beam-steering capability of the coding metasurface is implemented by encoding “0” and “1” elements with different phase responses and by controlling the coding sequences. The deflection angle can be controlled by changing the period of these 0 and 1 elements. Despite the development of beam-steering technology, measurements of the direction pattern of steered THz beams remain challenging. Systems for THz time-domain spectroscopy and spectral imaging are used to characterize the flexible coding metasurfaces. The THz imaging system can provide information on the directional pattern of the beam. To verify the performance of the proposed metasurface, the experimental measurements of beam deflection were found to be consistent with the values yielded by a simulation. Our study provides an effective platform for the design and measurement of THz beam steering.

Lidar system based on lens assisted integrated beam steering.

We present a demonstration of solid-state light detection and ranging (Lidar) at 1550 nm by applying integrated two-dimensional (2D) lens assisted beam-steering (LABS) technology. LABS has O(logN) power consumption for N antennas and allows a simple control complexity with digital signal input. A time-of-flight coaxial Lidar is demonstrated with this beam-steering technology. The integrated beam-steering chip and lens both transmit and receive the light. The Lidar has 16 scanning angles, 19.5 m ranging distance, and a 3 cm ranging error. This Letter proves the potential application of 2D LABS in Lidar and paves the way for a fully integrated Lidar system.