Subwavelength Bessel beams in wire media

Abstract

Recent progress is emerging on nondiffracting subwavelength fields propagating in complex plasmonic nanostructures. In this paper, we present a thorough discussion on diffraction-free localized solutions of Maxwell's equations in a periodic structure composed of nanowires. This self-focusing mechanism differs from others previously reported, which lie on regimes with ultraflat spatial dispersion. By means of the Maxwell-Garnett model, we provide a general analytical expression of the electromagnetic fields that can propagate along the direction of the cylinder's axis, keeping its transverse waveform unaltered. Numerical simulations based on the finite element method support our analytical approach. In particular, moderate filling fractions of the metallic composite lead to nonresonant-plasmonic spots of light propagating with a size that remains far below the limit of diffraction.

Nanolithography using Bessel Beams of Extreme Ultraviolet Wavelength

“…The Bessel beam is the simplest form of a nondiffracting beam, where its amplitude is proportional to the zeroth-order Bessel function of the first kind, which is a sharp peak surrounded by rings, not changing along the propagation axis 4 . Approximations to nondiffracting Bessel beams have been experimentally observed by focusing a Gaussian wave with an axicon lens 12 , using annular slits in the far field 1 , holographic methods 13 , by use of metamaterials and nanowire media 14 15 , and by circularly symmetric diffraction gratings 16 . Depending on the synthesis method, the beam can be chromatic or achromatic 12 .…”