Miniaturizing color-sensitive photodetectors via hybrid nanoantennas toward submicrometer dimensions.

Digital camera sensors use color filters on photodiodes to achieve color selectivity. As the color filters and photosensitive silicon layers are separate elements, these sensors suffer from optical cross-talk, which sets limits to the minimum pixel size. Here, we report hybrid silicon-aluminum nanostructures in the extreme limit of zero distance between color filters and sensors.

Schrödinger's red pixel by quasi-bound-states-in-the-continuum.

While structural colors are ubiquitous in nature, saturated reds are mysteriously absent. This long-standing problem of achieving Schrödinger's red demands sharp transitions from "stopband" to a high-reflectance "passband" with total suppression of higher-order resonances at blue/green wavelengths. Current approaches based on nanoantennas are insufficient to satisfy all conditions simultaneously.

Silicon Nanoantenna Mix Arrays for a Trifecta of Quantum Emitter Enhancements.

Dielectric nanostructures have demonstrated optical antenna effects due to Mie resonances. Previous work has exhibited enhancements in absorption, emission rates and directionality with practical limitations. In this paper, we present a Si mix antenna array to achieve a trifecta enhancement of ∼1200-fold with a Purcell factor of ∼47.

Ultraviolet Interband Plasmonics With Si Nanostructures.

Although Si acts as an electrical semiconductor, it has properties of an optical dielectric. Here, we revisit the behavior of Si as a plasmonic metal. This behavior was previously shown to arise from strong interband transitions that lead to negative permittivity of Si across the ultraviolet spectral range.

Structural color three-dimensional printing by shrinking photonic crystals.

The coloration of some butterflies, Pachyrhynchus weevils, and many chameleons are notable examples of natural organisms employing photonic crystals to produce colorful patterns. Despite advances in nanotechnology, we still lack the ability to print arbitrary colors and shapes in all three dimensions at this microscopic length scale. Here, we introduce a heat-shrinking method to produce 3D-printed photonic crystals with a 5x reduction in lattice constants, achieving sub-100-nm features with a full range of colors.

Wide-Gamut Plasmonic Color Palettes with Constant Subwavelength Resolution.

Unlike dye-based colorants, for which dilution results in a decrease in color saturation, a reduction of nanostructure density in plasmonic prints could increase color saturation instead. This interesting observation can be explained by the absorption cross-section of the nanostructure being larger than its physical cross-section. In this paper, we demonstrate the correlation between absorption cross-section and nanostructure density and use it to realize saturated colors by fabricating metal-insulator-metal aluminum nanostructures that support gap-surface plasmons (GSPs).

Highly Directive Hybrid Metal-Dielectric Yagi-Uda Nanoantennas.

A hybrid metal-dielectric nanoantenna promises to harness the large Purcell factor of metallic nanostructures while taking advantage of the high scattering directivity and low dissipative losses of dielectric nanostructures. Here, we investigate a compact hybrid metal-dielectric nanoantenna that is inspired by the Yagi-Uda design. It comprises a metallic gold bowtie nanoantenna feed element and three silicon nanorod directors, exhibiting high unidirectional in-plane directivity and potential beam redirection capability in the visible spectral range.

Printing Beyond sRGB Color Gamut by Mimicking Silicon Nanostructures in Free-Space.

Localized optical resonances in metallic nanostructures have been increasingly used in color printing, demonstrating unprecedented resolution but limited in color gamut. Here, we introduce a new nanostructure design, which broadens the gamut while retaining print resolution. Instead of metals, silicon nanostructures that exhibit localized magnetic and electric dipole resonances were fabricated on a silicon substrate coated with a SiN index matching layer.

On the correlation of absorption cross-section with plasmonic color generation.

Through numerical simulations, we investigate the correlation between the absorption cross-section and the color saturation of plasmonic nanostructures of varying density. Understanding this correlation, enables the prediction of an optimal nanostructure separation, or combinations of different nanostructure sizes for plasmonic color printing applications. Here, we use metal-insulator-metal (MIM) aluminum nanostructures that support gap-plasmons.

A Nanowire-Based Plasmonic Quantum Dot Laser.

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength.