Emiliano Di Gennaro

Experimental evidence of cut-wire-induced enhanced transmission of transverse-electric fields through sub-wavelength slits in a thin metallic screen

Recent numerical studies have demonstrated the possibility of achieving substantial enhancements in the transmission of transverse-electric-polarized electromagnetic fields through subwavelength slits in a thin metallic screen by placing single or paired metallic cut-wire arrays at a close distance from the screen. In this paper, we report on the first experimental evidence of such extraordinary transmission phenomena, via microwave (X/Ku-band) measurements on printed-circuit-board prototypes. Experimental results agree very well with full-wave numerical predictions, and indicate an intrinsic robustness of the enhanced transmission phenomena with respect to fabrication tolerances and experimental imperfections.

Superlensing properties of one-dimensional dielectric photonic crystals

We present the experimental observation of the superlensing effect in a slab of a one-dimensional photonic crystal made of tilted dielectric elements. We show that this flat lens can achieve subwavelength resolution in different frequency bands. We also demonstrate that the introduction of a proper corrugation on the lens surface can dramatically improve both the transmission and the resolution of the imaged signal.

Control of the light transmission through a quasiperiodic waveguide.

We studied the waveguiding properties of a photonic quasicrystal based on an octagonal tiling. The structure exhibits intrinsic localisation in the band gap region, that can be exploited to manipulate the signal transmission through a linear defect. The electromagnetic characteristics are first numerically analysed using a full wave simulation and then experimentally verified by measurements carried out in the X-band microwave region. Possible photonic applications include tunable notch filters having large attenuation.

Paired Cut-Wire Arrays for Enhanced Transmission of Transverse-Electric Fields Through Subwavelength Slits in a Thin Metallic Screen

It has recently been shown that the transmission of electromagnetic fields through subwavelength slits (parallel to the electric field direction) in a thin metallic screen can be greatly enhanced by covering one side of the screen with a metallic cut-wire array laid on a dielectric layer. In this Letter, we show that a richer phenomenology (which involves both electric- and magnetic-type resonances) can be attained by pairing a second cut-wire array at the other side of the screen. Via a full-wave comprehensive parametric study, we illustrate the underlying mechanisms and explore the additional degrees of freedom endowed, as well as their possible implications in the engineering of enhanced transmission phenomena.

Bandgap isotropy in photonic quasicrystals with low-index contrast

Formation and development of the photonic band gap in two-dimensional 8-, 10-, and 12-fold symmetry quasicrystalline lattices of low-index contrast are reported. Finite-size structures made of dielectric cylindrical rods are studied and measured in the microwave region, and their properties are compared with a conventional hexagonal crystal. Band-gap characteristics are investigated by changing the direction of propagation of the incident beam inside the crystal. Various angles of incidence are used to investigate the isotropic nature of the band gap.