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Design of a Broadband Metasurface Luneburg Lens for Full-Angle Operation
摘要： We present a broadband metasurface Luneburg lens for full-angle operation. The design of the Luneburg lens is based on an inverted substrate parallel-plate-waveguide structure with nonuniform circular holes etched on the upper metallic plate. We show that this structure is superior to existing designs as it allows significant simplification of the fabrication process. To achieve a smooth variation of the effective refractive index profile as well as circular symmetry for the Luneburg lens, size-variable meta atoms are used for synthesizing the metasurface. The effective refractive index profile can be tuned by varying just the hole diameters. By introducing tapered microstrip ports that are evenly distributed on the circumference of the Luneburg lens, full-angle operation of the lens can be achieved. A prototype with a diameter of 400 mm is fabricated and experimentally evaluated at operating frequencies ranging from 6 GHz to 9 GHz. We show good conceptual agreement between simulated and experimental results.
关键词： metasurface,inverted substrate parallel-plate-waveguide,Luneburg lens,Full-angle operation
更新于2025-09-23 15:23:52
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Realization of modified Luneburg lens antenna using quasi-conformal transformation optics and additive manufacturing
摘要： We demonstrate a new method for realizing modified Luneburg lens antennas with nearly continuously graded permittivity profiles in three-dimensions. The method used a quasi-conformal transformation optics (QCTO) approach to modify the geometry and permittivity of a spherical Luneburg lens to have a flat surface for convenient integration of antenna feeds. The modified lens was then fabricated using Fused Deposition Modeling (FDM) printing with an effective media approach that employs space-filling curves. The method was validated by designing and fabricating a modified Luneburg lens antenna designed to operate in the Ka-band. The antenna performance of the sample was measured experimentally and shown to compare well to predicted results using full wave simulations. The device was able to achieve a reasonably high degree of beam steering (ie, ?55° to +55°) over the entire Ka-band. We believe this new approach provides a cost-effective and scalable means of realizing practical passive beam steering lenses that operate over a broad range of frequencies.
关键词： additive manufacturing,beamscanning,beamforming,fused deposition modeling,Luneburg lens,transformation optics
更新于2025-09-23 15:22:29
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A Luneburg lens for spin waves
摘要： We report on the theory of a Luneburg lens for forward-volume magnetostatic spin waves and verify its operation via micromagnetic modelling. The lens converts a plane wave to a point source, and vice versa, by a designed graded refractive index, realized by modulating either the thickness or the saturation magnetization in a circular region. We ?nd that the lens enhances the wave amplitude by about 5 times at the lens focus, and 47% of the incident energy arrives in the focal region. A lens with small deviations from the optimal pro?le can still result in good focusing if the index is graded smoothly.
关键词： graded refractive index,Luneburg lens,micromagnetic modelling,spin waves
更新于2025-09-23 15:21:21
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Ultrashort waveguide tapers based on Luneburg lens
摘要： In integrated photonic circuits, silicon-on-insulator waveguides with different geometries have been employed to realize a variety of components. Therefore, efficient coupling of two different waveguides is crucial. In this paper, focusing property of the Luneburg lens is exploited to design waveguide tapers. The Luneburg lens, truncated in a shape of a parabolic taper with reduced footprint, is utilized to connect a 10 μm-wide waveguide to a 0.5 μm one with the same thickness with an average coupling loss of 0.35 dB in the entire O, E, S, C, L, and U bands of optical communications. The proposed compact taper with the length of 11 μm is implemented by varying the thickness of the guiding layer and compared with three conventional tapers with the same length. However, designing a coupler to connect waveguides with different thicknesses and widths is more challenging. By applying quasi-conformal transformation optics, we flatten the Luneburg lens and consequently increase the refractive index on the flattened side. As a result, we are able to couple two waveguides with different thicknesses and widths. The numerical simulations are used to evaluate the theoretically designed tapers. To our knowledge, this is the first study presenting ultrashort tapers based on truncated Luneburg lens.
关键词： Silicon-on-insulator,Waveguide taper,Metamaterials,Luneburg lens
更新于2025-09-23 15:19:57
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Coupling Between Silicon Waveguide and Metal-Dielectric-Metal Plasmonic Waveguide with Lens-Funnel Structure
摘要： Various photonic integrated components have been implemented by ultra-thin silicon-on-insulator (SOI) waveguides; therefore, it is desirable to couple ultra-thin SOI waveguides to plasmonic waveguides. In this paper, we present an ultra-thin SOI waveguide to a metal-dielectric-metal plasmonic waveguide based on a lens-funnel structure consisting of truncated Luneburg lens and metallic parabolic funnel. The lens is implemented by varying the guiding layer thickness. The effect of different parameters of the coupler’s geometry is studied using the finite-difference time-domain method. The 1.13-μm-long coupler improves the average coupling efficiency in the C-band from 66.4 to 82.1%. The numerical simulations indicate that the coupling efficiency is higher than 69% in the entire O, E, S, C, L, and U bands of optical communication.
关键词： Luneburg lens,Silicon-on-insulator,All-dielectric metamaterials,Plasmonic waveguide,Optical coupler,Strip waveguide
更新于2025-09-12 10:27:22
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Compact Air-filled Luneburg Lens Antennas Based on Almost-Parallel Plate Waveguide Loaded With Equal-Sized Metallic Posts
摘要： This paper presents a Luneburg lens and a Luneburg reflector-lens along with the corresponding compact and cost-effective multibeam antennas in the Ka-band. The Luneburg lens is composed of an air-filled parallel plate waveguide (PPW) loaded with equal-sized metallic posts. The upper plate of the PPW is designed to a curved surface to meet the requirement of the equivalent refractive index profile, meanwhile providing a transition between the lens and the feed waveguide. Also, based on the law of reflection, a reflecting wall is introduced to the Luneburg lens to achieve a Luneburg reflector-lens. By employing the WR28 rectangular waveguides as the feeders, the Luneburg lens/reflector-lens antennas with single beam and multiple beams are designed and experimentally verified in the whole Ka-band. The multibeam Luneburg lens antenna show the beam scanning from -45° to +45° with 0.6 dB scan loss. The multibeam Luneburg reflector-lens antenna show the beam scanning from 30° to 60° with 0.7 dB scan loss. Besides, the acceptable performances of aperture efficiency, impedance matching and multi-port isolation are achieved. The results indicate that the works in this paper have application potential in the millimeter-wave (mmW) wireless communications.
关键词： air-filled,Luneburg lens,Ka-band,multibeam antenna,Luneburg reflector-lens
更新于2025-09-11 14:15:04