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This study provides the design and demonstration of a Ku/K band horn‐fed linear polarization (LP) to circular polarization (CP) converter using a reflectarray antenna based on the holographic technique and the generalized law of total reflection without any iterative algorithms. The proposed hologram performs wide‐range frequency beam scanning with minimum gain losses and cross‐polarization levels. It comprises 2,500 diagonal slotted octagonal subwavelength metasurfaces with a periodicity of 0.266λ0 = 4 mm at 20 GHz as the center frequency. Two equations are defined to compute Y11 of the proposed unit cell regarding its dimensions for TE(0,0) and TM(0,0) Floquet modes. They significantly simplify the coding procedure and reduce the computational time for synthesizing the hologram. The antenna is simulated using the CST software from 14 to 25 GHz. As a confirmation, a prototype is manufactured and measured at 16, 18, 20, 22, and 24 GHz to verify its performance. The simulated and measured results are well‐matched. The presented hologram achieves 40% 1.8‐dB axial ratio (AR) bandwidth (16–25 GHz), 40% 3.3‐dB gain bandwidth (16–24 GHz), and above 30% 2‐dB gain bandwidth (16–22 GHz). Moreover, the antenna can perform beam scanning from 42° to 24° by changing the frequency from 16 to 24 GHz with peak gain values greater than 20.33 dBi. The LHCP pencil beams are at least 24° off‐broadside, so the proposed hologram avoids the feed blockage. These achievements make the hologram one of the best candidates for satellite communications, radar applications, short‐range communication, and point‐to‐point communication. Key Points: The antenna is designed based on the holographic technique and the law of total reflection for Ku and K band applicationsThe antenna frequency scans its main LHCP beam in a wide range with a high gain and low lossThe antenna performs LP to LHCP conversions with a wide axial ratio bandwidth and low cross‐polarization levels [ABSTRACT FROM AUTHOR]

• The passive structure of a fan-shaped holographic lens with different heights was developed to generate orbital angular momentum transferring acoustic vortices, resulting in acoustic trapping. • The helical acoustic vortices can be generated in the single-channel focused transducer by covering the lens. • Feasibility in acoustic trapping was investigated using several types of bioparticles (e.g., microbubbles, different sizes of polystyrene beads, and cancer cells). • The actuation mechanism of this approach is analyzed through understanding the relationship between drag and trapping forces. The utilization of acoustic vortices presents a promising technique for contactless particle manipulation. However, existing methods for generating acoustic vortices typically rely on complex active driving systems and array ultrasound transducers. Therefore, more simplified and robust approaches to inducing acoustic vortices should be considered. With inspiring the fact that acoustic vortices can be generated by the differences in the height of adjacent sectors in conventional four-panel transducers, we aim to develop a single-channel acoustic vortex tweezer with a simplified driving system by incorporating attachable fan-shaped polydimethylsiloxane (PDMS) holographic lens. This passive lens structure with different heights in adjacent sectors can generate phase-modulated ultrasonic waves. Therefore, the interaction of phase-modulated waves passing through the lens is expected to result in a vortex-like beam. The available materials of fan-shaped lens are not limited to the PDMS. This lens type can be appropriately fabricated with an understanding of the sound of speed within the desired material and predetermined thickness, inducing π/2 phase difference in the adjacent lobes. As a result, the excited acoustic waves propagated through the lens were under mutual interaction without any active electrical setup, forming a null pressure region enveloped by four distinct acoustic lobes. We systemically investigated the tweezing potential using vortex-like waves. Several types of bioparticles were utilized in these investigations: microbubbles, polystyrene (PS) beads, and cancer cells. Our findings demonstrate that the transducer with lens is sufficiently capable of spatial manipulation of bioparticles. Remarkably, the microbubbles traveling at a flow velocity of 32 cm/s in a blood vessel-mimicking phantom were feasibly trapped in the proposed transducer. Furthermore, the spatial control of PS and cells with higher acoustic impedance was also feasible in static conditions. Consequently, the proposed transducer offers an economically and practically viable solution for various biomedical applications, such as drug delivery and cell-based bioengineering. [Display omitted] [ABSTRACT FROM AUTHOR]

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This letter shows experimentally the realization of a high-gain multibeam bidirectional radiation in a wide frequency range via a planar holographic leaky-wave structure where the beams can scan from backward to forward direction as the frequency varies from 12 to 18 GHz. To realize these two key features, i.e., wideband characteristic and bidirectional multiple-beam pattern, we exploit the characteristic of a wideband surface wave launcher and inherent nature of a metasurface supporting TE mode at the same time. In more detail, this antenna benefits from a TE-mode antipodal Vivaldi as a distinguished feed, which has a broadband behavior, on a surface without metallic ground plane and realizes a high-gain bidirectional multibeam pattern. A four-beam linearly polarized antenna, including two backward and broadside beams in front side and two backward and broadside beams in the back side of the antenna is designed, fabricated, and tested at 12 GHz. The measured gain, sidelobe level, cross polarization, efficiency, and 3 dB bandwidth of the gain, are 17.8 dBi, −17 dB, −30 dB, 26.5%, and 43.3%, respectively, which are great achievements. Moreover, the maximum scan angle of $\text{44}^\circ $ , i.e., from $({\boldsymbol{\theta },\boldsymbol{\varphi }}) = ({\text{30}^\circ,180})\ $ to $({\boldsymbol{\theta },\boldsymbol{\varphi }}) = ({\text{14}^\circ,\text{0}^\circ})$ , is achieved for the backward beams when the frequency varies from f = 12 GHz to f = 18 GHz. [ABSTRACT FROM AUTHOR]

A multibeam radiator with each beam possessing independent polarization is developed by a single-feed holographic reflectarray (RA) antenna without using any optimization algorithms. Regardless of wave polarization, the relation between the electromagnetic properties of the antenna aperture (henceforth referred to as “hologram”) and impinging wave properties can be described by the holographic technique. For the practical implementation of such a hologram, we used a subwavelength metallic patch with anisotropic properties to satisfy the input admittance distribution of the hologram. In doing so, a fast numerical method, fundamentally inspired by the method of moments, is employed to calculate the input admittance of the element for all angles of incidence. This technique significantly speeds up the design process. Finally, as a typical case, a simple circularly polarized RA with four-beam radiation pattern was manufactured and tested at 13 GHz. The measured results showed that the aperture efficiency of 45.8%, cross-polarization discrimination of higher than 25 dB, 1 dB drop gain, 3 dB axial ratio bandwidths of 19.23% and 18.26%, sidelobe level of below −17 dB, and peak gain of around 19.43 dBi for each beam were obtained. [ABSTRACT FROM AUTHOR]

In this paper, a novel systematic method based on the holographic theory to design a reflectarray (RA) antenna is presented. According to the holographic technique, one can record features of electromagnetic waves impinging on a specific surface and then, whenever needed, reconstruct each of them. We exploit this property to design a single-feed RA with a multibeam linearly polarized pattern without using any iterative method such as optimization algorithms in the design process. At first, various kinds of interferograms along with related input admittance distributions are introduced according to the polarization and number of radiated beams. Afterward, a simple subwavelength metallic patch as a scalar admittance unit cell is employed to implement the input admittance distribution of the interferograms. Moreover, a fast analytical method, which is fundamentally inspired by the method of moments, has been employed to calculate the input admittance of the utilized element. Finally, as a typical case, an 18 cm $\times $ 18 cm linearly polarized RA with a two-beam radiation pattern has been manufactured and tested at 15 GHz. The sidelobe level, cross-pol, and efficiency of the antenna are found −26 dB, lower than −10 dB, and 47.2%, respectively, which meet the expectations. [ABSTRACT FROM AUTHOR]

For the first time, we present the design and demonstration of holographic transmitarray antennas (TAs) based on the susceptance (reactance) distribution in this paper. According to the holographic theory, the amplitudes and phases of electromagnetic waves can be recorded on a surface, and then they can be reconstructed independently. This concept is used to design single-beam and multi-beam linearly polarized holographic TAs without using any time-consuming optimization algorithms. Initially, an impedance surface is analyzed for both transmission and reflection modes. As there are differences between the susceptance (reactance) distribution of these modes, a new approach (different from reflectarray designs) is proposed to apply the holographic technique to transmitarray designs. Then, interferograms are described based on the scalar transmission susceptance distribution according to the number and direction of the radiation beams. Subsequently, a transmission metasurface of dimensions equal to 0.26 λ 0 is hired to design holographic TAs at 12 GHz. Several holograms are designed using the unit cell to verify the proposed method. Finally, as a proof of concept, a linearly polarized circular aperture wideband holographic transmitarray antenna with a radius of 13.3 cm is manufactured and tested. The antenna achieves 12.5% (11.4-12.9 GHz) 1-dB gain bandwidth and 23.8 dB maximum gain, leading to 21.46% aperture efficiency. Furthermore, the antenna achieves 95.94% simulated radiation efficiency mainly due to using subwavelength elements, which becomes possible by applying the holographic technique. [ABSTRACT FROM AUTHOR]

Laser-induced refractive index in fullerene-doped polyimide 6B has been investigated by the dynamic holographic technique. Nonlinear refractive index n2 and nonlinear optical susceptibility χ(3) of the compounds have been calculated. The role of spectral, thermal, and photorefractive effects in the holograpic grating recording under nano- and picosecond pulsed laser irradiation has been discussed. The place of the materials studied has been found among other nonlinear optical systems. [Copyright &y& Elsevier]

A three-dimensional complete bandgap (CBG) in the visible range is achieved by a self-similar spherical photonic crystal (PC) fabricated using the materials with low refractive index. A novel holographic technique is developed to fabricate such a structure. A CBG with a width of 120 nm is obtained experimentally. Even though the light not passing through the center of the sphere incidents on the PC with an incident angle of 49, a 30-nm-wide CBG can still be kept. Theoretical analysis is also given in which experimental results can be well explained. [ABSTRACT FROM PUBLISHER]

We present results that demonstrate the active management of eight ~100-GHz-spaced wavelength-division-multiplexed (WDM) channels using a polarization-insensitive spatial-light-modulator-based holographic filter. The filter has a fundamental stepping resolution close to 25 GHz and 3-dB width of each individual passband equal to 42 GHz. Arbitrary permutations of dropped and passed channels are possible. Additionally, passed channels can be transmitted according to an equal-amplitude comb filter function or be transmitted with weighted-amplitude passbands to effect power equalization where necessary. The holographic technique is further extendable to passband spectral engineering, yielding near-rectangular “top hat” passbands. Suppression of the dropped channels, which is consistently >15 dB in these experiments, can be straightforwardly improved by deploying a spatial light modulator of greater resolution and higher pixel number. The technology has potential application as the key element in both an optical add-drop multiplexer and a dynamic multichannel equalizer. The passband 3-dB width can be straightforwardly reduced to allow processing of multiple channels at the 50-GHz spacing of future WDM systems [ABSTRACT FROM PUBLISHER]