Vibrational Modes and Crystallographic Structure of Cd3As2 and (Cd1-xZnx)3As2 Epilayers

Low-temperature Raman scattering is used to study the crystal structure of molecular-beam epitaxially grown layers of the Dirac semimetal Cd3As2 and its related alloy (Cd1-xZnx)3As2. The combination of narrow-linewidth spectra, multiple growth directions and full polarization analysis allows improved accuracy in identifying the irreducible representation of over 57 Raman-active vibrations. Several disagreements with previous identifications are found. Structurally, the results agree with the centrosymmetric I41/acd space group of bulk-grown Cd3As2 and are clearly distinct from the Raman spectra of nanoscale platelets and wires. 3-fold twinning is seen in (112) Cd3As2 grown on (111) zincblende substrates corresponding to the three possible tetragonal orientations. In dilute (Cd1-xZnx)3As2, phonons have a frequency and scattering amplitude dependence on Zn concentration that is continuous with Cd3As2 but at least one frequency is absent at the alloy endpoint, preventing a simple one-mode description of the alloy phonon.

Design of reflective phase retarders in the extreme ultraviolet based on chirped Mo/Si multilayer mirrors

The extreme ultraviolet (EUV) phase retarder is an important optical element for polarization analysis and conversion of EUV synchrotron radiation. In this paper, a linearly chirped Mo/Si multilayer mirror is used to design an EUV phase retarder. With increasing thickness variation of the chirped multilayer, the reflective phase retardation between s- and p-polarized light increases at first and then reaches its maximum value. When the bilayer number increases from 2 to 20, the maximum phase retardation for an EUV source with a photon energy of 90 eV increases from 5.97° to 245.10° for a linearly chirped Mo/Si multilayer with 14.7 nm central thickness. In addition, the phase retardations of chirped mirrors at different photon energies (80 eV, 85 eV and 90 eV) are also investigated and compared. Furthermore, the physical mechanism of reflective phase retardation improvement is also studied by investigating the field intensity distributions inside chirped mirrors.

Jones matrix holography with metasurfaces

We propose a new class of computer-generated holograms whose far-fields have designer-specified polarization response. We dub these Jones matrix holograms. We provide a simple procedure for their implementation using form-birefringent metasurfaces. Jones matrix holography generalizes a wide body of past work with a consistent mathematical framework, particularly in the field of metasurfaces, and suggests previously unrealized devices, examples of which are demonstrated here. In particular, we demonstrate holograms whose far-fields implement parallel polarization analysis and custom waveplate-like behavior.