Interleaved coding Janus metasurface with independent transmission and reflection phase modulation.

An interleaved coding Janus metasurface is proposed, which can generate bidirectional functionalities with full phase control of the reflected and transmitted waves. By introducing rotation and geometric parameter changes into the meta-atoms, the reflection and transmission channels with required energy distribution and foci are realized. More remarkably, our approach is based on a single metasurface design that arranges two types of unidirectional propagating unit structures with simultaneous desired reflection and transmission properties into a checkerboard configuration to obtain four different holograms. The results verify the excellent performances of the multifunctional metasurface, laying a foundation for manipulation of EM waves with more degree of freedom, and promoting its applications in the entire frequency spectrum.

Using quasi-bound states in the continuum in an all-dielectric metasurface array to enhance terahertz fingerprint sensing.

The terahertz absorption fingerprint spectrum is crucial for qualitative spectral analysis, revealing the rotational or vibrational energy levels of numerous biological macromolecules and chemicals within the THz frequency range. However, conventional sensing in this band is hindered by weak interactions with trace analytes, leading to subtle signals. In this Letter, an all-dielectric metasurface array is proposed to enhance the absorption fingerprint spectrum using quasi-bound states in the continuum (BIC) resonance. The observable quasi-BIC resonance is achieved by breaking the symmetry of the C2v structure. The periodic dimensions of the structure are adjusted to excite quasi-BIC resonances at different frequencies, thereby enhancing the fingerprint spectra of four different substances. By exploiting the correlation between the Q-factor and absorption across different frequencies, calibration of the molecular absorption fingerprint spectrum obtained through metasurface sensing yields precise enhanced absorption fingerprint spectra for various substances within the 0.55-1.6 THz range. Our Letter introduces a novel, to the best of our knowledge, strategy for trace sensing in the THz frequency range, demonstrating the promising potential for enhanced absorption fingerprint spectrum sensing.

Design of an optically transparent and broadband absorber based on a multi-objective optimization algorithm.

In this Letter, an optically transparent and broadband absorber designed using a multi-objective genetic algorithm (MOGA) is proposed. The absorption of the multilayer lossy frequency selective surface-based absorber is calculated by multilayer absorption equations and equivalent circuit models. To solve the problem of the unbalanced structure absorption bandwidth and thickness, an algorithm is used for optimizing the geometric and sheet resistance parameters of the structure. A multilayer and optically transparent absorber with 90% absorption bandwidth covering a frequency range of 2-18 GHz (S-band to Ku-band) is developed based on the MOGA design method with optical transmittance of 60%. Its total thickness consists of a wavelength of only 0.095, and it has high oblique incidence stability, which makes it useful in the stealth technology and transparent electromagnetic shielding applications.

Observation of the bound states in the continuum supported by mode coupling in a terahertz metasurface.

Metasurface supporting bound states in the continuum (BIC) provides a unique approach for the realization of intense near-field enhancement and high quality factor (Q-factor) resonance, which promote the advancement of various applications. Here we experimentally demonstrate a Friedrich-Wintgen BIC based on the mode coupling in the terahertz metasurface, which produces BIC by the coupling of the LC mode and dipole mode resonances. The transition from ideal BIC to quasi-BIC is caused by the mismatch of the coupling, and the mode decay rate during this process is analyzed by temporal coupled mode theory. The Q-factor and the electric field enhancement of the quasi-BIC resonance are significantly increased, which provides enormous potential in sensing, nonlinear optics, and topological optics.

Dispersion engineering of spoof plasmonic metamaterials via interdigital capacitance structures.

This work presents an approach to realize the dispersion engineering of spoof plasmonic metamaterials with controllable cutoff frequencies. Interdigital capacitance structures are applied to construct the unit cells. Dispersion properties are firstly analyzed to investigate the effects of interdigital capacitance, and the influence of the geometrical parameters of the proposed unit cell on the cutoff frequencies is studied. Then, a spoof surface plasmon polariton (SSPP) transmission line (TL) is developed based on the proposed unit cell together with a smooth transition. The matching principles of the transition are explained by the dispersion curves and the normalized impedance of the corresponding matching unit cells. Finally, the transmission characteristics of the TL are simulated and measured to validate the feasibility of the proposed strategy. Both the lower and upper cutoff frequencies can be tuned jointly by the extra degrees of freedom provided by the interdigital capacitance structures. In comparison with designs based on a substrate-integrated waveguide (SIW), the proposed strategy can reduce the transversal dimension by a factor of two under the same conditions. This work can greatly accelerate the development of versatile microwave integrated circuits and systems based on spoof plasmonic metamaterials.

Design of a frequency-multiplexed metasurface with asymmetric transmission.

Metasurfaces presenting diversified functionalities have broadened the prospect of manipulating the phase, amplitude, and polarization from the optical to microwave fields. Although the frequency-multiplexing strategy is one of the intuitive and effective approaches to expand the number of channels, demonstrations reporting on the combination between directional asymmetric transmission and frequency-multiplexing via an ultrathin flat device are limited. In this study, a novel, to the best of our knowledge, strategy is proposed to generate four independent holographic images under opposite illumination directions at two operating frequencies, utilizing a single metasurface composed of two types of metallic resonators and one grating layer. Specifically, each scattering channel with independent information makes full use of the whole metasurface. Simulation and experimental results show good agreement, highlighting the attractive capabilities of the multi-functional metasurface platform, which provides more freedom for the manipulation of electromagnetic waves.

Identification and genomic characterization of major effect bacterial blight resistance locus (BB-13) in Upland cotton (Gossypium hirsutum L.).

KEY MESSAGE: Identification and genomic characterization of major resistance locus against cotton bacterial blight (CBB) using GWAS and linkage mapping to enable genomics-based development of durable CBB resistance and gene discovery in cotton. Cotton bacterial leaf blight (CBB), caused by Xanthomonas citri subsp. malvacearum (Xcm), has periodically been a damaging disease in the USA. Identification and deployment of genetic resistance in cotton cultivars is the most economical and efficient means of reducing crop losses due to CBB. In the current study, genome-wide association study (GWAS) of CBB resistance using an elite diversity panel of 380 accessions, genotyped with the cotton single nucleotide polymorphism (SNP) 63 K array, and phenotyped with race-18 of CBB, localized the CBB resistance to a 2.01-Mb region in the long arm of chromosome D02. Molecular genetic mapping using an F6 recombinant inbred line (RIL) population showed the CBB resistance in cultivar Arkot 8102 was controlled by a single locus (BB-13). The BB-13 locus was mapped within the 0.95-cM interval near the telomeric region in the long arm of chromosome D02. Flanking SNP markers, i04890Gh and i04907Gh of the BB-13 locus, identified from the combined linkage analysis and GWAS, targeted it to a 371-Kb genomic region. Candidate gene analysis identified thirty putative gene sequences in the targeted genomic region. Nine of these putative genes and two NBS-LRR genes adjacent to the targeted region were putatively involved in plant disease resistance and are possible candidate genes for BB-13 locus. Genetic mapping and genomic targeting of the BB13 locus in the current study will help in cloning the CBB-resistant gene and establishing the molecular genetic architecture of the BB-13 locus towards developing durable resistance to CBB in cotton.

Multi-band terahertz resonant absorption based on an all-dielectric grating metasurface for chlorpyrifos sensing.

Perfect metasurface absorbers play a significant role in imaging, detecting, and manipulating terahertz radiation. We utilize all-dielectric gratings to demonstrate tunable multi-band absorption in the terahertz region. Simulation reveals quad-band and tri-band absorption from 0.2 to 2.5 THz for different grating depths. Coupled-mode theory can explain the absorption phenomenon. The absorption amplitude can be precisely controlled by changing the pump beam fluence. Furthermore, the resonant frequency is sensitive to the medium's refractive index, suggesting the absorber may be of great potential in the sensor detection field. The experimental results exhibit a high detectivity of pesticides.

Short-circuited stub-loaded spoof surface plasmon polariton transmission lines with flexibly controllable lower out-of-band rejections.

This Letter proposes an approach to develop a spoof surface plasmon polariton (SSPP) transmission line (TL) by loading short-circuited (SC) shunt stubs. Lower out-of-band rejections can be flexibly controlled without affecting the upper cutoff frequency by independently modifying the stubs. Dispersion analysis of the SSPP unit is realized by theoretical calculation and circuit simulation to predict the upper cutoff frequency of the proposed SSPP TL simultaneously. Also, parametric sweeping of the SC shunt stubs is performed based on circuit simulation to investigate their impacts on the lower and upper out-of-band rejections of the proposed SSPP TL. In addition, electric field distributions of different types of TLs are simulated and compared to study the transmission characteristics of the proposed SSPP TL. The lower cutoff frequency can be flexibly tuned in a wide range, from 1.2 to 2.1 GHz, in the simulations. The measured 3-dB fractional bandwidth is about 128.1%, covering a range from 1.19 to 5.43 GHz. The numerical and experimental results are compatible, which verifies the feasibility of the proposed approach. This approach can offer more convenience and flexibility for controlling the rejections of the SSPP by introducing up to four tuning parameters. More importantly, the proposed SSPP TL avoids using the substrate integrated waveguide (SIW) technique, which shows the potential to decrease the transverse width (0.44λg), especially at lower frequencies (e.g., 1.2 GHz), and to reduce the complexity in designing the high-efficiency transition. This work paves the way for the development of novel SSPP-based microwave devices.

Generation and deflection control of a 2D Airy beam utilizing metasurfaces.

Self-accelerating optical Airy beams present attractive characteristics such as self-bending and non-diffraction, which have rendered this field a research hotspot in recent years. In this paper, the desired phase changes of the unit cell structure for the transmitted cross-polarized wave can be realized by modifying the rotation angle of the unit cell, while the amplitude can be modulated by changing the inner diameter R of the double layer split-ring resonator (SRR). As such, the amplitude and phase modulations can be performed simultaneously and independently to achieve the desired transmitted wave envelope. Furthermore, a novel, to the best of our knowledge, strategy of 2D Airy beam deflection control is also presented by simultaneously modifying the phase and amplitude of the envelope of the transmitted beam, and its feasibility is theoretically and experimentally demonstrated. Our proposed designs suggest high application potentials in the fields of optical particle manipulation, controllable wireless energy transmission, and complex terrain exploration.

Publisher Correction: Mixed matrix formulations with MOF molecular sieving for key energy-intensive separations.

In the version of this Article originally published, the units of the y axis of Fig. 3b were incorrectly given as '106 cm2 s-1'; they should have been '10-8 cm2 s-1'. This has been corrected in the online versions of the Article.

Helicity-switched hologram utilizing a polarization-free multi-bit coding metasurface.

In this work, a polarization-free coding metasurface is proposed to manipulate circularly polarized waves. Compared to a Pancharatnam-Berry phase metasurface, the proposed design not only allows for overcoming anti-symmetrical response characteristics between orthogonal circularly polarized states to enable achieving identical functionality under both right-handed and left-handed circularly polarized wave illuminations and avoiding polarization-conversion losses but also offers additional degree of freedom in the control of handedness. As a proof-of-concept demonstration, a polarization-free multi-bit coding metasurface is designed to realize helicity-switched holograms in the microwave region. Experimental measurements performed on a fabricated prototype reveal outstanding imaging quality with extremely high imaging efficiency above 76% for arbitrary polarizations at 10 GHz. Our proposed method expands the route in manipulating circularly polarized waves and can be applied over the whole electromagnetic spectrum for wavefront manipulation.

Polarization-multiplexed Huygens metasurface holography.

Huygens metasurface, as a subcategory of metamaterials, shows great potential in the capacity and efficiency of electromagnetic wave manipulation within a subwavelength scale. Here, the transmission-type Huygens metasurface is demonstrated for complete and independent control of orthogonally polarized transmitted waves by constructing pairs of crossed electric and magnetic resonances in three-sheet meta-atoms as the building blocks for holographic imaging. Under incoherent horizontally and vertically polarized illuminations, two designated holographic images with negligible mutual interferences are accomplished with at least 62.95% measured imaging efficiency and 63.53 signal-to-noise ratio, respectively. This work addresses several major issues in traditional polarization-multiplexed holography with regard to transmission-coefficient manipulation capacity, image fidelity, and simple fabrication technique, empowering advanced research and applications in polarization-selective microwave devices and information processing.

High-density linkage map construction and QTL analyses for fiber quality, yield and morphological traits using CottonSNP63K array in upland cotton (Gossypium hirsutum L.).

BACKGROUND: Improving fiber quality and yield are the primary research objectives in cotton breeding for enhancing the economic viability and sustainability of Upland cotton production. Identifying the quantitative trait loci (QTL) for fiber quality and yield traits using the high-density SNP-based genetic maps allows for bridging genomics with cotton breeding through marker assisted and genomic selection. In this study, a recombinant inbred line (RIL) population, derived from cross between two parental accessions, which represent broad allele diversity in Upland cotton, was used to construct high-density SNP-based linkage maps and to map the QTLs controlling important cotton traits. RESULTS: Molecular genetic mapping using RIL population produced a genetic map of 3129 SNPs, mapped at a density of 1.41 cM. Genetic maps of the individual chromosomes showed good collinearity with the sequence based physical map. A total of 106 QTLs were identified which included 59 QTLs for six fiber quality traits, 38 QTLs for four yield traits and 9 QTLs for two morphological traits. Sub-genome wide, 57 QTLs were mapped in A sub-genome and 49 were mapped in D sub-genome. More than 75% of the QTLs with favorable alleles were contributed by the parental accession NC05AZ06. Forty-six mapped QTLs each explained more than 10% of the phenotypic variation. Further, we identified 21 QTL clusters where 12 QTL clusters were mapped in the A sub-genome and 9 were mapped in the D sub-genome. Candidate gene analyses of the 11 stable QTL harboring genomic regions identified 19 putative genes which had functional role in cotton fiber development. CONCLUSION: We constructed a high-density genetic map of SNPs in Upland cotton. Collinearity between genetic and physical maps indicated no major structural changes in the genetic mapping populations. Most traits showed high broad-sense heritability. One hundred and six QTLs were identified for the fiber quality, yield and morphological traits. Majority of the QTLs with favorable alleles were contributed by improved parental accession. More than 70% of the mapped QTLs shared the similar map position with previously reported QTLs which suggest the genetic relatedness of Upland cotton germplasm. Identification of QTL clusters could explain the correlation among some fiber quality traits in cotton. Stable and major QTLs and QTL clusters of traits identified in the current study could be the targets for map-based cloning and marker assisted selection (MAS) in cotton breeding. The genomic region on D12 containing the major stable QTLs for micronaire, fiber strength and lint percentage could be potential targets for MAS and gene cloning of fiber quality traits in cotton.

Mixed matrix formulations with MOF molecular sieving for key energy-intensive separations.

Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal-organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO2 and H2S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures.

Coding Huygens' metasurface for enhanced quality holographic imaging.

In this paper, coding Huygens' metasurface (CHM) is proposed for holographic imaging with enhanced quality. A weighted holographic algorithm is used to calculate the phase distribution at the interface and to design the CHM. Experimental demonstration performed in the microwave region validates holographic imaging with the ability to modulate energy distribution among focal points and improve image quality. By judiciously engineering both electric and magnetic dipolar resonators, the proposed digital Huygens' meta-atom is able to provide a full transmission-phase covering the whole range of 2π together with a near-unity transmission efficiency. The proof-of-concept experiments show that holographic imaging quality can be indeed improved by using digital meta-atoms with several bits. Furthermore, the modulation of intensity distribution among focal points is experimentally realized by using the 3-bits CHM. The proposed CHM hologram shows great potential in a variety of application fields, such as programmable high-resolution imaging lenses, microscopy, data storage, information processing, and computer-generated holograms.

Multi-focus hologram utilizing Pancharatnam-Berry phase elements based metamirror.

An ultrathin reflection-type metamirror is proposed for multi-focusing with any desired focusing fashion including focal number and location. The metamirror is composed of reflection-type Pancharatnam-Berry (P-B) phase elements, which are able to provide full reflection phase of 2π, together with near-unity reflection efficiency by judiciously engineering the rotation angle of each latter element. A holographic algorithm is utilized to calculate the phase distribution at the interface of the metamirror to achieve the desired multi-focus spots. Experimental demonstrations performed in microwave region show good imaging quality with high reflection efficiency and imaging efficiency. The proposed metamirror provides a high-performance solution for low-cost and lightweight beam-shaping and beam-focusing devices.

Carbon Molecular Sieve Membrane Preparation by Economical Coating and Pyrolysis of Porous Polymer Hollow Fibers.

Dip coating and pyrolysis processes are used to create multi-layer asymmetric carbon molecular sieve (CMS) hollow fiber membranes with excellent gas separation properties. Coating of an economical engineered support with a high-performance polyimide to create precursor fibers with a dense skin layer reduces material cost by 25-fold compared to monolithic precursors or ceramic supports. CMS permeation results with CO2 /CH4 (50:50) mixed gas feed show attractive CO2 /CH4 selectivity of 58.8 and CO2 permeance of 310 GPU at 35 °C.

Experimental validation of active holographic metasurface for electrically beam steering.

In this paper, a holographic metasurface possessing beam scanning capability at fixed frequency is presented. The desired radiation beam is obtained by using a reference wave to excite a sinusoidally-modulated impedance surface, which is equivalent to the interference pattern between the radiation wave and reference wave. By changing the bias voltage of varactor diodes loaded on the sub-wavelength unit cells, the variation range of the modulated impedance can be tuned, resulting in the change of radiation angle. Both the simulation and experimental results demonstrate that the direction of the radiation beam can be tuned in the range from 23° to 50° at 5.5 GHz. The proposed holographic metasurface shows great potential applications in constructing planar beam scanning antenna for integrated microwave system.

Phase-engineered metalenses to generate converging and non-diffractive vortex beam carrying orbital angular momentum in microwave region.

In this paper, ultra-thin metalenses are proposed to generate converging and non-diffractive vortex beam carrying orbital angular momentum (OAM) in microwave region. Phase changes are introduced to the transmission cross-polarized wave by tailoring spatial orientation of Pancharatnam-Berry phase unit cell. Based on the superposition of phase profile of spiral phase plate and that of a converging lens or an axicon, vortex beam carrying OAM mode generated by the metalens can also exhibit characteristics of a focusing beam or a Bessel beam. Measured field intensities and phase distributions at microwave frequencies verify the theoretical design procedure. The proposed method provides an efficient approach to control the radius of vortex beam carrying OAM mode in microwave wireless applications for medium-short range distance.