Intrinsic and extrinsic chiral responses have been widely investigated in metamaterials, however the relationship between them has been seldom discussed. We numerically and experimentally demonstrate angle enhanced chiral dichroism and study the separation between intrinsic and extrinsic chiral responses in metamaterial with asymmetrically split aperture dimers. The metamaterial exhibits triple-band resonant circular dichroism at normal incidence. The oblique incidence leads to giant enhancement of circular dichroism at two low-frequency resonances while yields an obvious resonance split of the circular dichroism in the vicinity of the high-frequency resonance. The whole circular dichroism response results from the balance between intrinsic and extrinsic chirality and the circular dichroism spectra at positive and negative angles of incidence exhibit an asymmetry due to the existence of intrinsic chirality. Importantly, the intrinsic chirality in the metamaterial may be individually investigated since extrinsic chiral response may be removed from the total circular dichroism by superimposing two circular dichroism spectra at positive and negative incident angles. The metamaterial will be promising to achieve enhanced chiral response and also separately utilize intrinsic and extrinsic chirality for manipulating the polarization state of light.

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Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave. However, archiving transmissive coding metasurface is still challenging. Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations. The polarization beam splitter and the OAM generator have been studied as typical applications of anisotropic 2-bit coding metasurface. The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions, respectively. The anisotropic coding metasurface has been experimentally verified to realize an orbital angular momentum (OAM) beam with l = 2 of right-handed polarized wave, resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation. This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.

We intend to carry out a series of plasma lens experiments at the Final Focus Test Beam facility at SLAC. These experiments will be the first to study the focusing of particle beams by plasma focusing &vices in the parameter regime of interest for high energy colliders, and is expected to lead to plasma lens designs capable of unprecedented spot sizes. Plasma focusing of positron beams will be attempted for the first time. We will study the effects of lens aberrations due to various lens imperfections. Several approaches will be applied to create the plasma required including laser ionization and beam ionization of a working gas. At an increased bunch population of 2.5x lOlo, tunneling ionization of a gas target by an electron beam -an effect which has never been observed before -should be significant. The compactness of our device should prove to be of interest for applications at the SLC and the next generation linear colliders.

In the past few decades, the discovery of topological matter states has ushered in a new era in topological physics, providing a robust framework for strategically controlling the transport of particles or waves. Topological photonics, in particular, has sparked considerable research due to its ability to construct and manipulate photonic topological states via photonic artificial microstructures. Although the concept of topology originates from condensed matter, topological photonics has given rise to new fundamental ideas and a range of potential applications that may lead to revolutionary technologies. Here, we review recent developments in topological photonics, with a focus on the realization and application of several emerging research areas in photonic artificial microstructures. We highlight the research trend, spanning from the photonic counterpart of topological insulator phases, through topological semimetal phases, to other emerging non-Hermitian topologies.