An official website of the United States government
Metasurfaces have been continuously garnering attention in both scientific and industrial fields owing to their unprecedented wavefront manipulation capabilities using arranged subwavelength artificial structures. Terahertz vortex beams have become a focus of research in recent years due to their prominent role in many cutting-edge applications. However, traditional terahertz vortex beam plates are often faced with challenges including large size, low efficiency, and limited working bandwidth. Here, we propose and experimentally demonstrate highly efficient and broadband vortex beam plates based on metasurface in the terahertz region. The experimental results well verify that the designed metasurfaces can efficiently generate terahertz vortex beams with different orbital angular momentum topological charges in the range of 0.5–1 THz. Notably, the maximum efficiency can reach about 65% at 0.5 THz. The proposed devices may play a vital role in developing vortex beams-related terahertz applications.
more »
« less
This content will become publicly available on October 23, 2026
Generation of non-diffractive terahertz Bessel beams using 3D printed spiral zone plates
Due to their unique non-diffracting properties, Bessel beams have been studied across microwave to optical frequency regimes. Although several schemes for generating Bessel beams at microwave and terahertz (THz) frequencies have been demonstrated, these works have mainly focused on symmetric Bessel beams with little attention being given to asymmetric forms. In addition, existing methods are often technically involved, bulky, and costly. To address the gap in the generation of asymmetric beams and the identified challenges with contemporary generation schemes, we show that it is possible to produce both asymmetric and symmetric Bessel beams in a relatively simple and cost-effective manner using a planar Archimedean spiral zone plate. We fabricate this device using 3D printing and use it as a Bessel beam launcher operating at 0.2 THz. The zone plate generates an asymmetric Bessel beam close to the aperture through superposition of Bessel modes. As the axial distance is increased, the beam evolves into a symmetric Bessel beam.
more »
« less
- PAR ID:
- 10696496
- Publisher / Repository:
- AIP Publishing
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 127
- Issue:
- 17
- ISSN:
- 0003-6951
- Page Range / eLocation ID:
- 171102
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Andrews, D; Galvez, E; Rubinsztein-Dunlop (Ed.)Einstein beams are coherent optical beams generated by the conditions of gravitational lensing. In the ray picture, Einstein beams are formed by the intersection of light rays deflected by a lensing mass, similar to nondiffracting Bessel beams, but with the difference that adjacent rays diverge slightly. When accounting for the wave properties of light, they form beam-like diffraction patterns that preserve their shape but expand as the light propagates. The addition of a topological charge to the light, leads to more complex patterns carrying orbital angular momentum. For symmetric lensing conditions, Einstein beams carry modes described by confluent hypergeometric functions, which can be approximated by Bessel functions. A theoretical analysis of this is presented here. In astrophysical observations, many of these features can only be inferred because conditions of coherence and alignment make them difficult to observe. Studies of Einstein beams in the laboratory can be used to inform astrophysical observations and discover new non-astrophysical laboratory applications.more » « less
-
Communication in the terahertz (THz) frequency band is a key focus for the next generation of wireless systems, in part because of the possibility for enhanced security in combination with ultra-high data rates. To enable communication links in the presence of blockage of a directional line-of-sight beam, self-accelerating THz beams have recently been proposed. For such beams, the main lobe radiated from an aperture follows some engineered curved trajectory in the electromagnetic near field. Self-accelerating beams enable advantages unlike traditional beams by curving around potential eavesdroppers located in the vicinity of the radiating aperture. Here, we theoretically and experimentally analyze the security implications of such beams by evaluating their secrecy capacity. We also explore the implications of blockage and self-healing on this security metric.more » « less
-
Abstract The large available bandwidth at sub-terahertz and terahertz frequencies has the potential to enable very high data rates for wireless communications. Moreover, given the large electrical size of terahertz antenna apertures, many future terahertz communication systems will likely operate in the near field. However, due to their reliance on highly directional beams, terahertz systems are susceptible to blockage. Here, we propose using Bessel beams to overcome issues caused by blockage due to their diffraction-free nature and self-healing properties in the near field. We compare the performance of information-bearing Bessel beams and Gaussian beams with and without an obstacle. We later discuss the use of reconfigurable intelligent surfaces to construct terahertz Bessel beams. Finally, we propose a metric to quantify the quality of imperfectly generated terahertz Bessel beams and explore their ability to self-heal. The results demonstrate that Bessel beams are an attractive option for near-field terahertz communications, especially when mitigating the effects of partial blockage.more » « less
-
Abstract Here we present a machine learning–based wind reconstruction model. The model reconstructs hurricane surface winds with XGBoost, which is a decision-tree-based ensemble predictive algorithm. The model treats the symmetric and asymmetric wind fields separately. The symmetric wind field is approximated by a parametric wind profile model and two Bessel function series. The asymmetric field, accounting for asymmetries induced by the storm and its ambient environment, is represented using a small number of Laplacian eigenfunctions. The coefficients associated with Bessel functions and eigenfunctions are predicted by XGBoost based on storm and environmental features taken from NHC best-track and ERA-Interim data, respectively. We use HWIND for the observed wind fields. Three parametric wind profile models are tested in the symmetric wind model. The wind reconstruction model’s performance is insensitive to the choice of the profile model because the Bessel function series correct biases of the parametric profiles. The mean square error of the reconstructed surface winds is smaller than the climatological variance, indicating skillful reconstruction. Storm center location, eyewall size, and translation speed play important roles in controlling the magnitude of the leading asymmetries, while the phase of the asymmetries is mainly affected by storm translation direction. Vertical wind shear impacts the asymmetry phase to a lesser degree. Intended applications of this model include assessing hurricane risk using synthetic storm event sets generated by statistical–dynamical downscaling hurricane models.more » « less
