A SIMPLIFIED PARAMETER DESIGN METHOD FOR TRANSFORMATION OPTICS-BASED METAMATERIAL INNOVATIVE CLOAK

Transformation optics-based innovative cloak which combines the virtues of both internal and external cloaks to enable arbitrary multi-objects hidden with visions and movements was first proposed by Huang et al. [Appl. Phys. Lett.101, 151901 (2012)]. But it is rather difficult to implement in practice, for the required material parameters vary with radius and even have singular values. To accelerate its practical realization but still keep good performance of invisibility, a simplified innovative cloak with only spatially varying axial parameter is developed via choosing appropriate transformation function. The advantage of such a cloak is that both radial and azimuthal parameters are constants, and all three components are nonsingular and finite. Full-wave simulation confirms the perfect cloaking effect of the cloak. Besides, the influences of metamaterials loss and parameter deviation on the performance of cloak are also investigated. This work provides a simple and feasible solution to push metamaterial-assisted innovative cloak more closely to the practice.

Electromagnetic Reciprocal Cloak with Only Axial Material Parameter Spatially Variant

Reciprocal cloak is an intriguing metamaterial device, in which a hidden antenna or a sensor can receive electromagnetic irradiation from the outside but its presence will not be detected. Based on transformation optics, a cylindrical electromagnetic reciprocal cloak with only axial parameter varying with radius is designed and validated by full wave simulation. When two dispersive reciprocal cloaks are put together, they do not interfere with each other. Our work demonstrates the electromagnetic compatibility (EMC) ability of the reciprocal cloak which is very important in multi antenna and sensor design.

Eisenionen als Spinsonden in CdGa2S4-Kristallen / Fe(III) Ions as Spin Probes in CdGa2S4 Crystals

In EPR studies on Fe(III) ions in CdGa2S4 crystals, in accordance with the two different Ga sites two paramagnetic centers could be detected which differ widely in their axial parameter D. An investigation of the crystal field allowed a unique site assignment. A comparison with the Fe(III) resonances in CuGaS2 and AgGaS2 does show that the superposition model of Newman and Urban cannot be applied to CdGa2S4 with similar parameters as in the chalcopyrite structures. - A characteristic twinning could be revealed, similar to the “reversed cubic structure” in sphalerite.

EPR of Fe3+ in Low Quartz Isomorphs A(III)B(V)O4

Electron spin resonance spectra of Fe3+ in hydrothermally grown single crystals of AlPO4 , GaPO4, AlASO4 and GaAsO4 were measured at X-band and analyzed using a Spin-Hamiltonian for rhombic symmetry. The zero field splitting was found to be between about one and two times the microwave frequency, increasing regularly from AlPO4 to GaAsO4. This increase is largely due to an increase in the axial parameter D whereas the second order rhombic parameter E is practically constant. The fourth order parameter a increases exponentially with the lattice parameter ratio c0/a0 . The variation of D indicates a site distortion for GaPO4 about twice as large as in AlPO4 . For the arsenates, influences of increased covalency are apparent in addition to site distortions of comparable size. Halfwidths in the range of 18 Gauss for the phosphates and 38 Gauss for the arsenates indicate hyperfine interactions with 31P and 75As, and estimates of 0.5 and 1% spin density resp. at these nuclei are obtained, again showing increased covalency for the arsenate compounds.