We study the diffraction of electromagnetic waves from subwavelength metallic circular apertures in the microwave spectrum. The theoretical and experimental demonstration of the near- and far-field electromagnetic distributions for subwavelength circular annular apertures and circular annular apertures surrounded by concentric periodic grooves are reported here. The metallic samples had a subwavelength hole with a diameter of 8 mm and had concentric grooves with a periodicity of 16 mm. We present the angular transmission distributions from circular annular apertures, and circular annular apertures surrounded by concentric periodic grooves. At the surface-mode resonance frequency the transmitted electromagnetic waves from the subwavelength circular annular aperture surrounded by concentric periodic grooves have a strong angular confinement with an angular divergence of ±3°. This represents a fourfold reduction when compared with the angular divergence of the beam transmitted from the subwavelength circular aperture.
© 2006 Optical Society of America
Original Manuscript: July 5, 2005
Manuscript Accepted: August 21, 2005
Humeyra Caglayan, Irfan Bulu, and Ekmel Ozbay, "Beaming of electromagnetic waves emitted through a subwavelength annular aperture," J. Opt. Soc. Am. B 23, 419-422 (2006)