David A. Powell
YOU?
Author Swipe
View article: Switched-beam antennas based on achromatic Huygens metalenses for broadband beamforming and directional reception
Switched-beam antennas based on achromatic Huygens metalenses for broadband beamforming and directional reception Open
Achromatic metalenses offer promising solutions for advanced wireless systems by enabling compact, high-gain, and directive beamforming capabilities based on switched-beam antenna techniques. Conventional metalenses, however, are prone to …
View article: Analytical design of acoustic metasurface cells incorporating meander-line and Helmholtz resonators
Analytical design of acoustic metasurface cells incorporating meander-line and Helmholtz resonators Open
Gradient acoustic metasurfaces have shown strong potential for manipulation of acoustic waves across the audible and ultrasonic frequency ranges. The key challenge in designing acoustic metasurfaces is to create a series of sub-wavelength …
View article: Exceptional energy harvesting from coupled bound states
Exceptional energy harvesting from coupled bound states Open
Sustainable and affordable energy is one of the most critical issues facing society. Noise is ubiquitous, albeit with a low energy density, making it an almost perfect energy source. Bound states in the continuum overcome this problem thro…
View article: Analytical design of acoustic metasurface cells incorporating meander-line and Helmholtz resonators
Analytical design of acoustic metasurface cells incorporating meander-line and Helmholtz resonators Open
Gradient acoustic metasurfaces have shown strong potential for manipulation of acoustic waves across the audible and ultrasonic frequency ranges. The key challenge in designing acoustic metasurfaces is to create a series of sub-wavelength …
View article: Reconfigurable Manipulation of Sound with a Multimaterial 3D Printed Origami Metasurface
Reconfigurable Manipulation of Sound with a Multimaterial 3D Printed Origami Metasurface Open
The challenge in reconfigurable manipulation of sound waves using metasurfaces lies in achieving precise control over acoustic behavior while developing efficient and practical tuning methods for structural configurations. However, most st…
View article: Reconfigurable Acoustic Metalens with Tailored Structural Equilibria
Reconfigurable Acoustic Metalens with Tailored Structural Equilibria Open
The ability to concentrate sound energy with a tunable focal point is essential for a wide range of acoustic applications, offering precise control over the location and intensity of sound pressure maxima. However, conventional acoustic me…
View article: Shape optimized acoustic metagratings for anomalous refraction under strong thermoviscous effects
Shape optimized acoustic metagratings for anomalous refraction under strong thermoviscous effects Open
The recent development of microacoustic metagratings opens up promising possibilities for manipulating acoustic wavefronts passively, particularly in applications such as flat acoustic lenses and ultra-high frequency ultrasound imaging. Th…
View article: Exceptional energy harvesting from coupled bound states
Exceptional energy harvesting from coupled bound states Open
Sustainable and affordable energy is one of society's most critical issues. Noise is ubiquitous and disruptive, hence a near-perfect energy harvesting source, albeit with a low energy density. To overcome the problem of low energy density,…
View article: Reconfigurable Manipulation of Sound with a Multi-material 3D-Printed Origami Metasurface
Reconfigurable Manipulation of Sound with a Multi-material 3D-Printed Origami Metasurface Open
The challenge in reconfigurable manipulation of sound waves using metasurfaces lies in achieving precise control over acoustic behavior while developing efficient and practical tuning methods for structural configurations. However, most st…
View article: Broadband noise-insulating periodic structures made of coupled Helmholtz resonators
Broadband noise-insulating periodic structures made of coupled Helmholtz resonators Open
Acoustic metamaterials and phononic crystals represent a promising platform for the development of noise-insulating systems characterized by a low weight and small thickness. Nevertheless, the operational spectral range of these structures…
View article: Modelling of layered surface acoustic wave resonators for liquid media sensing applications
Modelling of layered surface acoustic wave resonators for liquid media sensing applications Open
In this thesis a model is developed to characterise the behaviour of layered SAW 2- port resonator sensors operating in liquid media. In the critical review of literature, it is found that methods based on the periodic Green's function com…
View article: Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices
Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices Open
Quasi-bound states in the continuum (QBICs) coupling into the propagating spectrum manifest themselves as high-quality factor (Q) modes susceptible to perturbations. This poses a challenge in predicting stable Fano resonances for realistic…
View article: Sound attenuation enhancement of acoustic meta-atoms via coupling
Sound attenuation enhancement of acoustic meta-atoms via coupling Open
Arrangements of acoustic meta-atoms, better known as acoustic metamaterials, are commonly applied in acoustic cloaking, for the attenuation of acoustic fields or for acoustic focusing. A precise design of single meta-atoms is required for …
View article: Ultra-broadband Noise-Insulating Periodic Structures Made of Coupled Helmholtz Resonators
Ultra-broadband Noise-Insulating Periodic Structures Made of Coupled Helmholtz Resonators Open
Acoustic metamaterials and phononic crystals represent a promising platform for the development of noise-insulating systems characterized by a low weight and small thickness. Nevertheless, the operational spectral range of these structures…
View article: Direct visualization of a Friedrich-Wintgen quasi-bound state in the continuum
Direct visualization of a Friedrich-Wintgen quasi-bound state in the continuum Open
Bound states in the continuum (BICs) are a well known phenomenon in physics, particularly in quantum physics and wave physics. Since BICs are local states, their existence typically manifests as Fano resonances in the transmission or refle…
View article: Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices - Data & Codes
Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices - Data & Codes Open
We have added all the necessary data to reproduce the results presented in our manuscript. The codes for plotting the pressure field mappings and the transmission spectrum are MATLAB-based. We have also added a Python routine for modal dec…
View article: Planar Metasurface Antenna with Tunable via Boundaries for Computational Imaging
Planar Metasurface Antenna with Tunable via Boundaries for Computational Imaging Open
The fusion of metasurface antennas and computational imaging facilitates the design of microwave imaging systems which require no lenses, phase shifters or moving parts. The technique involves the generation of appropriately designed diver…
View article: Metahouse: Noise‐Insulating Chamber Based on Periodic Structures
Metahouse: Noise‐Insulating Chamber Based on Periodic Structures Open
Noise pollution remains a challenging problem requiring the development of novel systems for noise insulation. Extensive work in the field of acoustic metamaterials has led to various ventilated structures which, however, are usually demon…
View article: A General Framework of Bound States in the Continuum in an Open Acoustic Resonator
A General Framework of Bound States in the Continuum in an Open Acoustic Resonator Open
Bound states in the continuum (BICs) provide a viable way of achieving high-Q resonances in both photonics and acoustics. In this work, we proposed a general method of constructing Friedrich-Wintgen (FW) BICs and accidental BICs in a coupl…
View article: Microacoustic Metagratings at Ultra‐High Frequencies Fabricated by Two‐Photon Lithography (Adv. Sci. 20/2022)
Microacoustic Metagratings at Ultra‐High Frequencies Fabricated by Two‐Photon Lithography (Adv. Sci. 20/2022) Open
Microacoustic Metagratings In article number 2200990, Anton Melnikov and co‐workers present microacoustic metagratings for passive wavefront manipulation of ultra‐high frequency ultrasound. The designs are created with topology and shape o…
View article: Topological Supercavity Resonances in the Finite System
Topological Supercavity Resonances in the Finite System Open
Acoustic resonant cavities play a vital role in modern acoustical systems. The ultrahigh quality‐factor resonances are highly desired for some applications such as high‐resolution acoustic sensors and acoustic lasers. Here, a class of supe…
View article: Microacoustic Metagratings at Ultra‐High Frequencies Fabricated by Two‐Photon Lithography
Microacoustic Metagratings at Ultra‐High Frequencies Fabricated by Two‐Photon Lithography Open
The recently proposed bianisotropic acoustic metagratings offer promising opportunities for passive acoustic wavefront manipulation, which is of particular interest in flat acoustic lenses and ultrasound imaging at ultra‐high frequency ult…
View article: Microacoustic metagratings at ultra-high frequencies fabricated by two-photon lithography
Microacoustic metagratings at ultra-high frequencies fabricated by two-photon lithography Open
The recently proposed bianisotropic acoustic metagratings offer promising opportunities for passive acoustic wavefront manipulation, which is of particular interest in flat acoustic lenses and ultrasound imaging at ultra-high frequency ult…
View article: Topological Supercavity Resonances In the Finite System
Topological Supercavity Resonances In the Finite System Open
Acoustic resonant cavities play a vital role in modern acoustical systems. They have led to many essential applications for noise control, biomedical ultrasonics, and underwater communications. The ultrahigh quality-factor resonances are h…
View article: Scalable Metagrating for Efficient Ultrasonic Focusing
Scalable Metagrating for Efficient Ultrasonic Focusing Open
Acoustic focusing plays a pivotal role in a wide variety of applications ranging from medical science to nondestructive testing. Previous works have shown that acoustic metagratings can overcome the inherent efficiency limitations of gradi…
View article: Characterization of Broadband Focusing Microwave Metasurfaces at Oblique Incidence
Characterization of Broadband Focusing Microwave Metasurfaces at Oblique Incidence Open
We report the characterization of an achromatic focusing metasurface at oblique incident angles. We show that in addition to the inherent off-axis aberrations that occurs due to the hyperbolic phase profile of the metasurface, the focusing…
View article: Willis coupling-induced acoustic radiation force and torque reversal
Willis coupling-induced acoustic radiation force and torque reversal Open
Acoustic meta-atoms serve as the building blocks of metamaterials, with linear properties designed to achieve functions such as beam steering, cloaking and focusing. They have also been used to shape the characteristics of incident acousti…
View article: Printed Tapered Leaky-Wave Antennas for W-Band Frequencies
Printed Tapered Leaky-Wave Antennas for W-Band Frequencies Open
Despite their great potential in communication and sensing applications, printed leaky-wave antennas have rarely been reported at mm-wave frequencies. In this paper, tapered leaky-wave antennas operating at 80 GHz are designed, fabricated …
View article: Sound Trapping in an Open Resonator
Sound Trapping in an Open Resonator Open
The ability of extreme sound energy confinement with high-quality factor (Q-factor) resonance is of vital importance for acoustic devices requiring high intensity and hypersensitivity in biological ultrasonics, enhanced collimated sound em…
View article: Characterization of Broadband Focusing Microwave Metasurfaces at Oblique\n Incidence
Characterization of Broadband Focusing Microwave Metasurfaces at Oblique\n Incidence Open
We report the characterization of an achromatic focusing metasurface at\noblique incident angles. We show that in addition to the inherent off-axis\naberrations that occurs due to the hyperbolic phase profile of the metasurface,\nthe focus…