Dual-polarized Response Research Articles

Polarization imaging and edge detection with image-processing metasurfaces

Optical metasurfaces have been recently explored as ultrathin analog image differentiators. By tailoring the momentum transfer function, they can perform efficient Fourier filtering—and thus potentially any linear mathematical operation—on an input image, replacing bulky 4f systems. While this approach has been investigated in different platforms, and a few techniques have been explored to achieve the required angular response, little effort has been devoted so far to tailor and control also the polarization response of an image-processing metasurface. Here, we show that edge-detection metasurfaces can be designed with tailored polarization responses, while simultaneously preserving an isotropic response. In particular, we demonstrate numerically and experimentally single-layer silicon metasurfaces yielding efficient Laplacian operation on a 2D image with either large polarization asymmetry, or nearly polarization-independent response. In the former case, we show that a strongly asymmetric polarization response can be used to unlock more sophisticated on-the-fly image processing functionalities, such as dynamically tunable direction-dependent edge detection. In parallel, metasurfaces with dual-polarized response are shown to enable efficient operation for unpolarized or arbitrarily polarized images, ensuring high efficiency. For both devices, we demonstrate edge detection within relatively large numerical apertures and with excellent isotropy and intensity throughput. Our study paves the way for the broad use of optical metasurfaces for sophisticated, massively parallel analog image processing with zero energy requirements.

A double-layer Huygens’ metasurface with complete phase coverage and its dual-polarized meta-lens antenna application

A novel double-layer Huygens’ unit with dual-polarized response and complete phase coverage has been proposed for highly efficient meta-lens antenna application. The designed unit is a symmetric structure in which the double-layer metallic patterns not only act as the electric dipoles but also induce the magnetic dipoles. The balance between the initial electric dipole and the induced magnetic dipole makes the impedance of the metasurface match with that of free space, thus allowing efficient transmission of electromagnetic waves. Moreover, full transmission phase shift and near-unit transmission amplitude can be achieved simultaneously by change the structural parameters of the unit. Utilizing such electromagnetic properties, a dual-polarized meta-lens consisting of 35 × 35 units with size of 161 × 161 mm2 is designed, fabricated and measured. The results exhibit its good radiation performance. The maximum gain at a frequency of 28 GHz reaches 30.8 dBi, with an aperture efficiency of 42.3%. The 3-dB gain bandwidth reaches 12.5%, covering the frequency range of 26.7–30.2 GHz. The simple structure of the designed dual-polarized metasurface, high gain and high antenna efficiency make it an important antenna engineering role.

Low profile polarization‐insensitive wideband rasorber with in‐band transmission

A dual-polarized wide-band rasorber with in-band transmission has been presented in this study. Our proposed design comprises a modified swastika design on the upper layer and a square slotted design on the bottom layer. The top layer is loaded with lumped resistors on the top pattern in an even manner resulting in broadband absorption. The square slot designed on the lower layer is accountable for in-the-band transmission. The total thickness of the design is only 0.058 λL (λL corresponds to the lowest frequency) and possesses strong fractional bandwidth of around 124%. The whole design shows a wideband absorption whose reflection coefficient is less than −10 dB from 1.7 to 7.25 GHz, and an insertion loss of 0.6 dB in the transmission band at 4.9 GHz. The originality of the proposed design lies in its miniaturized design, good angular stability, high fractional bandwidth, and dual-polarized response. For a comprehensive analysis, we have investigated the distribution of surface current, its corresponding circuit model, and several other parameters. Finally, the prototype has been fabricated and validated, it has been found that there is a decent agreement between measured and simulated responses.

Diagonally Fed Square Microstrip Antenna for Wideband Dualpolarized Response

A novel method of increasing the length of surface current distributions to enhance the bandwidth of a microstrip antenna is proposed in this paper. Introduction of sinusoidal perturbations and additional stubs along the edges of a square microstrip antenna with diagonal feed reduces the frequency of the higher order TM11 mode towards the frequency of fundamental mode of the patch by increasing the path lengths of surface current yielding a band width of nearly 46.5%. Proposed antenna exhibits broadside radiation pattern at the band edge frequencies of the impedance locus. Dual polarized response is realized in the proposed configuration by embedding two asymmetric slots that causes degeneration of fundamental mode.

Dual Polarized Multiband Stub and Slot Loaded Semicircular Microstrip Antenna

A multiband configuration using semicircular patch fabricated on glass epoxy at height of 1.58mm was reported. The patch was loaded with a stub and a slot. Three bands were observed respectively at 3.5GHz with gain of 1.5dBi due to patch, 2.45 GHz with gain of 1.2dBi due to stub and 5.5GHz with gain of 1.8dBi due to slot. However detailed explanation of various resonant modes for getting multiband dual polarized response was not given in the reported work. In this paper a detailed analysis using resonance curve plots, return loss plot and vector surface current distributions explaining the multiband dual polarized response of reported work is presented. It is observed that length variations of stub and slot modify various modes of semicircular patch in such a way that results into multiband band dual polarized response. The dimension along with position of slot and stub with given feed location causes matching input impedances of TM10, TM31 and TM32 modes which results in multiband dual polarized response.

Design of Compact F-shape Microstrip Antenna For Dual Polarized Broadband Response

Design of compact multiple slots cut F-shape microstrip antenna for broadband dual polarized response is presented. The multiple rectangular slots in F-shape patch, tunes the resonance frequency and impedance at second order TM20 mode with reference to the fundamental TM10 mode, that yields bandwidth of more than 500 MHz (>40%). Because of orthogonal current variations across TM10 and TM20 modes, F-shape patch yields dual polarized wideband response. The bandwidth of individual polarization is governed by the stub length in F-shape patch. Proposed antenna exhibits broadside radiation pattern over the bandwidth with gain of more than 6 dBi at two resonant modes.