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1. Beam steering at the nanosecond time scale with an atomically thin reflector

   https://doi.org/10.1038/s41467-022-29976-0  

   Andersen, Trond I.; Gelly, Ryan J.; Scuri, Giovanni; Dwyer, Bo L.; Wild, Dominik S.; Bekenstein, Rivka; Sushko, Andrey; Sung, Jiho; Zhou, You; Zibrov, Alexander A.; et al (June 2022, Nature Communications)

   Abstract Techniques to mold the flow of light on subwavelength scales enable fundamentally new optical systems and device applications. The realization of programmable, active optical systems with fast, tunable components is among the outstanding challenges in the field. Here, we experimentally demonstrate a few-pixel beam steering device based on electrostatic gate control of excitons in an atomically thin semiconductor with strong light-matter interactions. By combining the high reflectivity of a MoSe₂monolayer with a graphene split-gate geometry, we shape the wavefront phase profile to achieve continuously tunable beam deflection with a range of 10°, two-dimensional beam steering, and switching times down to 1.6 nanoseconds. Our approach opens the door for a new class of atomically thin optical systems, such as rapidly switchable beam arrays and quantum metasurfaces operating at their fundamental thickness limit. 

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2. Reconfigurable Intelligent Surface Design for Enhanced Beam Steering in Communication Systems

   https://doi.org/10.23919/INC-USNC-URSI61303.2024.10632285  

   Islam, T; Eroglu, A; Jones, M; Henao, M; Hackenbruch, C; Xie, Z (July 2024, IEEE)

   This paper presents a reconfigurable intelligent surface (RIS) design and simulation aimed at enhancing beamforming and beam steering capabilities for 5G and 6G mobile communications. The proposed design introduces a 2- bit unit cell design, having four distinct phase states that can be tuned by a single varactor diode. This configuration has a 5x5 array and provides efficient operation at 23.8 GHz within the 5G New Radio (NR) frequency range 2 (FR2). The proposed RIS design demonstrates unique beam steering capabilities ranging from −60∘ to 60∘ in the azimuth plane which is crucial for extending coverage into the mm-wave coverage. The performance of the RIS is simulated using the CST 3D electromagnetic simulator, focusing on radar cross section (RCS) pattern for optimization. The simulation results reveal effective beam steering capabilities ranging from -10° to -60° and 10° to 60°, with a minimum scan loss of approximately 3 dB. The proposed RIS exhibits the high angular reciprocity that handles the incident waves up to 110∘ at an oblique 60∘ angle. 

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3. Liquid-crystal-based visible-light integrated optical phased arrays and application to underwater communications

   https://doi.org/10.1364/OL.494387  

   Notaros, Milica; DeSantis, Daniel_M; Raval, Manan; Notaros, Jelena (October 2023, Optics Letters)

   In this Letter, we present the first, to the best of our knowledge, liquid-crystal-based integrated optical phased arrays (OPAs) that enable visible-light beam forming and steering. A cascaded OPA architecture is developed and experimentally shown to emit a beam in the far field at a 632.8-nm wavelength with a power full width at half maximum of 0.4°×1.6° and 7.2° beam-steering range within ±3.4 V. Furthermore, we show the first visible-light integrated-OPA-based free-space-optical-communications transmitter and use it to demonstrate the first integrated-OPA-based underwater-wireless-optical-communications link. We experimentally demonstrate a 1-Gbps on–off-keying link through water and an electronically-switchable point-to-multipoint link with channel selectivity greater than 19 dB through a water-filled tank. 

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4. Mm-Wave Beam Steering Antennas Using Stacked Parallel Plate Lens Antenna Subarrays

   https://doi.org/10.1109/USNC-URSI52151.2023.10237493  

   Jebreil, Omar; Mumcu, Gokhan (July 2023, IEEE)

   A millimeter (mm)-wave beam steering antenna consisting of subarrays of parallel plate lenses is presented for the first time. As compared to a previously reported antenna that utilized subarrays of dielectric slab waveguide lenses, the presented antenna allows to design and control the beamwidth of the radiation pattern in the plane orthogonal to the beam steering plane by stacking the parallel plate lens subarrays. Additionally, full wave simulations of the presented antenna show performance improvements in gain, side lobe level, and field of view in comparison to the previously reported dielectric slab waveguide-based realization. 

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5. Realization of a wide steering end-fire facet optical phased array using silicon rich silicon nitride

   https://doi.org/10.1364/OL.476819  

   Nejadriahi, Hani; Gaur, Prabhav; Johnson, Karl; Pappert, Steve; Fainman, Yeshaiahu; Yu, Paul (January 2023, Optics Letters)

   The design, fabrication, and characterization of a 16-element optical phased array (OPA) using a high index (n = 3.1) silicon-rich silicon nitride (SRN) is demonstrated. We present one-dimensional beam steering with end-fire facet antennas over a wide steering range of >115° at a fixed wavelength of 1525 nm. A beam width of 6.3° has been measured at boresight, consistent with theory. We demonstrate SRN as a viable material choice for chip-scale OPA applications due to its high thermo-optic coefficient, high optical power handling capacity [negligible two-photon absorption (TPA)], wide transparency window, and CMOS compatibility. 

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