Beam-Size Invariant Spectropolarimeters Using Gap-Plasmon Metasurfaces

Metasurfaces enable exceptional control over the light with surface-confined planar components, offering the fascinating possibility of very dense integration and miniaturization in photonics. Here, we design, fabricate and experimentally demonstrate chip-size plasmonic spectropolarimeters for simultaneous polarization state and wavelength determination. Spectropolarimeters, consisting of three gap-plasmon phase-gradient metasurfaces that occupy 120{\deg} circular sectors each, diffract normally incident light to six predesigned directions, whose azimuthal angles are proportional to the light wavelength, while contrasts in the corresponding diffraction intensities provide a direct measure of the incident polarization state through retrieval of the associated Stokes parameters. The proof-of-concept 96-{\mu}m-diameter spectropolarimeter operating in the wavelength range of 750-950nm exhibits the expected polarization selectivity and high angular dispersion. Moreover, we show that, due to the circular-sector design, polarization analysis can be conducted for optical beams of different diameters without prior calibration, demonstrating thereby the beam-size invariant functionality. The proposed spectropolarimeters are compact, cost-effective, robust, and promise high-performance real-time polarization and spectral measurements

Direct amplitude-phase near-field observation of higher-order anapole states

Anapole states associated with the resonant suppression of electric-dipole scattering exhibit minimized extinction and maximized storage of electromagnetic energy inside a particle. Using numerical simulations, optical extinction spectroscopy and amplitude-phase near-field mapping of silicon dielectric disks, we demonstrate high-order anapole states in the near-infrared wavelength range (900-1700 nm). We develop the procedure for unambiguously identifying anapole states by monitoring the normal component of the electric near-field and experimentally detect the first two anapole states as verified by far-field extinction spectroscopy and confirmed with the numerical simulations. We demonstrate that higher order anapole states possess stronger energy concentration and narrower resonances, a remarkable feature that is advantageous for their applications in metasurfaces and nanophotonics components, such as non-linear higher-harmonic generators and nanoscale lasers

High-efficiency silicon metasurface mirror on a sapphire substrate

For a possible implementation of high-efficiency Si-nanosphere metasurface mirrors functioning at telecom wavelengths in future gravitational wave detectors, exact dimensional and configuration parameters of the total system, including substrate and protective coating, have to be determined a priori. The reflectivity of such multi-layer metasurfaces with embedded Si nanoparticles and their potential limitations need to be investigated. Here we present the results on how the substrate and protective layer influence optical properties and demonstrate how dimensional and material characteristics of the structure alter light reflectivity. Additionally, we consider the impact of manufacturing imperfections, such as fluctuations of Si nanoparticle sizes and their exact placement, on the metasurface reflectivity. Finally, we demonstrate how high reflectivity of the system can be preserved under variations of the protective layer thickness, incident angle of light, and its polarization

Sintering oxide ceramics based on AI[2]O[3] and ZrO[2], activated by MgO, TiO[2] and SiO[2] additives

The positive effect of the addition of MgO and TiO[2] in an amount of no more than 1 wt. % on sintering and physico-mechanical properties of alumina ceramics is established. Addition of 5% of SiO[2] to A1[2]O[3] provides the mechanism of liquid phase sintering of ceramics, which leads to increase in its density and strength up to 480 MPa. In ceramic system A1[2]O[3] - ZrO[2] - Y[2]O[3] highest level of physical and mechanical properties of the composition had a hypereutectic composition 16.6% A1[2]O[3] - 76% Z1O[2] - 7.4% Y[2]O[3]. In this composition two mechanisms of hardening are realized simultaneously, such as transformational hardening by t-m -ZrO[2] transition and dispersion strengthening with high-modulus particles of [alpha]- A1[2]O[3]