On-Chip Detection of Optical Spin-Orbit Interactions in Plasmonic Nanocircuits.

On-chip manipulating and controlling the temporal and spatial evolution of light are of crucial importance for information processing in future planar integrated nanophotonics. The spin and orbital angular momentum of light, which can be treated independently in classical macroscopic geometrical optics, appear to be coupled on subwavelength scales. We use spin-orbit interactions in a plasmonic achiral nanocoupler to unidirectionally excite surface plasmon polariton modes propagating in seamlessly integrated plasmonic slot waveguides. The spin-dependent flow of light in the proposed nanophotonic circuit allows on-chip electrical detection of the spin state of incident photons by integrating two germanium-based plasmonic-waveguide photodetectors. Consequently, our device serves as a compact (∼6 × 18 µm2) electrical sensor for photonic spin Hall dynamics. The demonstrated configuration opens new avenues for developing highly integrated polarization-controlled optical devices that would exploit the spin-degree of freedom for manipulating and controlling subwavelength optical modes in nanophotonic systems.

Laser Writing of Bright Colors on Near-Percolation Plasmonic Reflector Arrays.

Coloration by surface nanostructuring has attracted a great deal of attention by the virtue of making use of environment-friendly recyclable materials and generating nonbleaching colors. Recently, it was found possible to delegate the task of color printing to laser postprocessing that modifies carefully designed and fabricated nanostructures. Here we take the next crucial step in the development of structural color printing by dispensing with preformed nanostructures and using instead near-percolation metal films atop dielectric-metal sandwiches, that is, near-percolation plasmonic reflector arrays. Scanning rapidly (∼20 µm/s) across 4 nm-thin island-like gold films supported by 30 nm-thin silica layers atop 100 nm-thick gold layers with a strongly focused Ti-sapphire laser beam, while adjusting the average laser power from 1 to 10 mW, we produce bright colors varying from green to red by laser-heating-induced merging and reshaping of gold islands. Selection of strongly heated islands and their reshaping, both originating from excitation of plasmonic resonances, are strongly influenced by the polarization direction of laser illumination, so that the colors produced are well pronounced only when viewed with the same polarization. Conversely, the laser color writing with circular polarizations results in bright polarization-independent color images. The fabrication procedure for near-percolation reflector arrays is exceedingly simple and scalable to mass production, while the laser-induced modification occurs inherently with the subwavelength resolution. This combination of features makes the approach developed for laser color writing readily amenable for practical implementation and use in diverse applications ranging from nanoscale patterning for security marking to large-scale color printing for decoration.

Near-infrared tailored thermal emission from wafer-scale continuous-film resonators.

We experimentally investigate the near-infrared emission from simple-to-fabricate, continuous-film Fabry-Perot-type resonators, consisting only of unstructured dielectric and metallic films. We show that the proposed configuration is suitable for realization of narrowband emitters, tunable in ranges from mid- to near-infrared, and demonstrate emission centered at the wavelength of 1.7 µm, which corresponds to the band gap energy of GaSb-based photodetectors. The emission is measured at 748 K and follows well the emissivity as predicted from reflection measurements and Kirchhoff's reciprocity. The considered emitter configuration is spectrally highly tunable and, consisting of only few unstructured layers, is amenable to wafer-scale fabrication at low cost by use of standard deposition procedures.

Subwavelength plasmonic color printing protected for ambient use.

We demonstrate plasmonic color printing with subwavelength resolution using circular gap-plasmon resonators (GPRs) arranged in 340 nm period arrays of square unit cells and fabricated with single-step electron-beam lithography. We develop a printing procedure resulting in correct single-pixel color reproduction, high color uniformity of colored areas, and high reproduction fidelity. Furthermore, we demonstrate that, due to inherent stability of GPRs with respect to surfactants, the fabricated color print can be protected with a transparent dielectric overlay for ambient use without destroying its coloring. Using finite-element simulations, we uncover the physical mechanisms responsible for color printing with GPR arrays and suggest the appropriate design procedure minimizing the influence of the protection layer.