the electromagnetic waves and thus enables versatile functionalities in a planar structure. [15,16] To date, a majority of the studies have been focused on plasmonic metasurfaces involving metallic elements. A prime example is the metasurface composed of spatially varying metallic scatters distributed in one direction. However, plasmonic metasurfaces are difficult to move beyond the limitations of the inherent Ohmic losses and the orthogonal polarization conversion efficiency. [17,18] Efforts have been made to increase the polarization conversion efficiency [10,[19][20][21][22] or to avoid polarization conversion (Huygens surface) by employing multilayer plasmonic metasurfaces, [17,[23][24][25][26][27][28] but these designs introduce other problems. For example, extra loss from dielectric spacers is brought in. Meanwhile, the multilayer design becomes complex and also increases the fabrication challenges.Recently, all-dielectric metasurfaces have drawn enormous attentions. Free from the material loss, all-dielectric metasurfaces have been demonstrated to be able to manipulate lightmatter interactions and manifest exotic photonic behavior with a very high efficiency, far beyond their metallic counterparts. [29] For efficient wavefront engineering, dielectric metasurfaces also play an essential role by utilizing simultaneous excitation of Mie-type electric and magnetic resonances, [30,31] or effective waveguiding effect, [32,33] or the geometric phase concept. [34][35][36] Furthermore, to maximize the usability, controlling the polarization dependence is usually considered in the design. [35][36][37][38][39] However, such studies on dielectric metasurfaces for efficient wavefront engineering thus far, are mainly performed at optical and infrared frequencies. [40] With the rapid development of terahertz technology, the terahertz regime is also in great demand for various highly efficient, flexible, and low-cost functional devices, where the use of the all-dielectric metasurface is a promising solution.In this article, we numerically and experimentally demonstrate polarization-dependent, transmission-type all-silicon dielectric metasurfaces for manipulation of terahertz wavefront. The proposed polarization-dependent metasurface functions as two different devices with respect to the x-and y-polarizations. An efficiency around 60% could be achieved for both the Recently, metasurfaces made up of dielectric structures have drawn enormous attentions in the optical and infrared regimes due to their high efficiency and designing freedom in manipulating light propagation. Such advantages can also be introduced to terahertz frequencies where efficient functional devices are still lacking. Here, polarization-dependent all-silicon terahertz dielectric metasurfaces are proposed and experimentally demonstrated. The metasurfaces are composed of anisotropic rectangular-shaped silicon pillars on silicon substrate. Each metasurface holds dual different functions depending on the incident polarizations. Furthermore, to suppress the r...

Polarization, which represents the vector nature of electromagnetic waves, plays a fundamental role in optics. Fast, simple, and broadband polarization state characterization is required by applications such as polarization communication, polarimetry, and remote sensing. However, conventional polarization detection methods face great difficulty in determining the phase difference between orthogonal polarization states and often require a series of measurements. Here, we demonstrate how polarization-dependent holography enables direct polarization detection in a single measurement. Using a multiplexed Pancharatnam-Berry phase metasurface, we generate orthogonally polarized holograms that partially overlap with a spatially varying phase difference. Both amplitude and phase difference can be read from the holographic image in the circular polarization basis, facilitating the extraction of all Stokes parameters for polarized light. The metahologram detects polarization reliably at several near-infrared to visible wavelengths, and simulations predict broadband operation in the 580-940 nm spectral range. This method enables fast and compact polarization analyzing devices, e.g., for spectroscopy, sensing, and communications.

Surface plasmon polaritons (SPPs) with the features of subwavelength confinement and strong enhancements have sparked enormous interest. However, in the terahertz regime, due to the perfect conductivities of most metals, it is hard to realize the strong confinement of SPPs, even though the propagation loss could be sufficiently low. One main approach to circumvent this problem is to exploit spoof SPPs, which are expected to exhibit useful subwavelength confinement and relative low propagation loss at terahertz frequencies. Here we report the design, fabrication, and characterization of terahertz spoof SPP waveguides based on corrugated metal surfaces. The various waveguide components, including a straight waveguide, an S-bend waveguide, a Y-splitter, and a directional coupler, were experimentally demonstrated using scanning near-field terahertz microscopy. The proposed waveguide indeed enables propagation, bending, splitting, and coupling of terahertz SPPs and thus paves a new way for the development of flexible and compact plasmonic circuits operating at terahertz frequencies.

A luminol electrochemiluminescence assay was reported to analyze active cholesterol at the plasma membrane in single mammalian cells. The cellular membrane cholesterol was activated by the exposure of the cells to low ionic strength buffer or the inhibition of intracellular acyl-coA/cholesterol acyltransferase (ACAT). The active membrane cholesterol was reacted with cholesterol oxidase in the solution to generate a peak concentration of hydrogen peroxide on the electrode surface, which induced a measurable luminol electrochemiluminescence. Further treatment of the active cells with mevastatin decreased the active membrane cholesterol resulting in a drop in luminance. No change in the intracellular calcium was observed in the presence of luminol and voltage, which indicated that our analysis process might not interrupt the intracellular cholesterol trafficking. Single cell analysis was performed by placing a pinhole below the electrode so that only one cell was exposed to the photomultiplier tube (PMT). Twelve single cells were analyzed individually, and a large deviation on luminance ratio observed exhibited the cell heterogeneity on the active membrane cholesterol. The smaller deviation on ACAT/HMGCoA inhibited cells than ACAT inhibited cells suggested different inhibition efficiency for sandoz 58035 and mevastatin. The new information obtained from single cell analysis might provide a new insight on the study of intracellular cholesterol trafficking.

FIG. 4. Simulation and experimental results of sample 6. (a) Transmission, (b) PCR, and (c) phase difference between u and v polarizations.

Y, et al. (2017) Alldielectric meta-holograms with holographic images transforming longitudinally. ACS Photonics.

Previously, our group has utilized the luminol electrochemiluminescence to analyze the active cholesterol at the plasma membrane in single cells by the exposure of one cell to a photomultiplier tube (PMT) through a pinhole. In this paper, fast analysis of active cholesterol at the plasma membrane in single cells was achieved by a multimicroelectrode array without the pinhole. Single cells were directly located on the microelectrodes using cell-sized microwell traps. A cycle of voltage was applied on the microelectrodes sequentially to induce a peak of luminescence from each microelectrode for the serial measurement of active membrane cholesterol. A minimal time of 1.60 s was determined for the analysis of one cell. The simulation and the experimental data exhibited a semisteady-state distribution of hydrogen peroxide on the microelectrode after the reaction of cholesterol oxidase with the membrane cholesterol, which supported the relative accuracy of the serial analysis. An eight-microelectrode array was demonstrated to analyze eight single cells in 22 s serially, including the channel switching time. The results from 64 single cells either activated by low ion strength buffer or the inhibition of intracellular acyl-coA/cholesterol acyltransferase (ACAT) revealed that most of the cells analyzed had the similar active membrane cholesterol, while few cells had more active cholesterol resulting in the cellular heterogeneity. The fast single-cell analysis platform developed will be potentially useful for the analysis of more molecules in single cells using proper oxidases.

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