Maize is an important crop with a high level of genome diversity and heterosis. The genome sequence of a typical female line, B73, was previously released. Here, we report a de novo genome assembly of a corresponding male representative line, Mo17. More than 96.4% of the 2,183 Mb assembled genome can be accounted for by 362 scaffolds in ten pseudochromosomes with 38,620 annotated protein-coding genes. Comparative analysis revealed large gene-order and gene structural variations: approximately 10% of the annotated genes were mutually nonsyntenic, and more than 20% of the predicted genes had either large-effect mutations or large structural variations, which might cause considerable protein divergence between the two inbred lines. Our study provides a high-quality reference-genome sequence of an important maize germplasm, and the intraspecific gene order and gene structural variations identified should have implications for heterosis and genome evolution.

We demonstrate enormously strong chiral effects from a photonic metamaterial consisting of an array of dual-layer twisted-arcs with a total thickness of ∼ λ/6. Experimental results reveal a circular dichroism of ∼ 0.35 in the absolute value and a maximum polarization rotation of ∼ 305°/λ in a near-infrared wavelength region. A transmission of greater than 50% is achieved at the frequency where the polarization rotation peaks. Retrieved parameters from measured quantities further indicate an actual optical activity of 76° per λ and a difference of 0.42 in the indices of refraction for the two circularly polarized waves of opposite handedness.

A chiral metamaterial produces both distinguishable linear and non-linear resonant features when probed with left and right circularly polarized light. The material demonstrates a linear transmission contrast of 0.5 between left and right circular polarizations and a 20× contrast between second-harmonic responses from the two incident polarizations. Non-linear and linear response images probed with circularly polarized light show strongly defined contrast.

We present dynamic tuning and symmetry lowering of Fano resonances in gold heptamers accomplished by applying uniaxial mechanical stress. The flexible heptamer structure was obtained by embedding the seven-gold-nanocylinder complex in a polydimethylsiloxane membrane. Under uniaxial stress, the Fano resonance exhibited opposite spectral shifts for the two orthogonal polarizations parallel and perpendicular to the mechanical stress. Furthermore, a new resonance was observed for polarization parallel to the mechanical stress but not for the perpendicular polarization. The experimental results showed good agreement with the numerical simulations. A detailed group theoretical analysis showed that the symmetry lowering caused by the mechanical stress not only splits the originally degenerate mode but also modifies the originally optically inactive mode into an optically active mode, which then interacts strongly with a closely spaced mode and exhibits anticrossing behavior. The symmetry tuning enabled by applying mechanical stress is a simple and efficient way to engineer the nature of coupled plasmon resonances in complex nanostructures. The mechanically tunable plasmonic nanostructures also provide an excellent platform for dynamically tunable nanophotonic devices such as tunable filters and sensors.

Metamaterials have not only enabled unprecedented flexibility in producing unconventional optical properties that are not found in nature, they have also provided exciting potential to create customized nonlinear media with high-order properties correlated to linear behaviour. Two particularly compelling directions are active metamaterials, whose optical properties can be purposely tailored by external stimuli in a reversible manner, and nonlinear metamaterials, which enable intensity-dependent frequency conversion of light waves. Here, by exploring the interaction of these two directions, we leverage the electrical and optical functions simultaneously supported in nanostructured metals and demonstrate electrically controlled nonlinear optical processes from a metamaterial. Both second harmonic generation and optical rectification, enhanced by the resonance behaviour in the metamaterial absorber, are modulated externally with applied voltage signals. Our results reveal an opportunity to exploit optical metamaterials as self-contained, dynamic electro-optic systems with intrinsically embedded electrical functions and optical nonlinearities.