Caglayan, H.Bulu, I.Özbay, Ekmel2016-02-082016-02-0820060740-3224http://hdl.handle.net/11693/23879We 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.EnglishElectromagnetic wave diffractionElectromagnetic wave emissionElectromagnetic wave transmissionMicrowave spectroscopyAngular transmission distributionsFar-field electromagnetic distributionsMicrowave spectrumNear-field electromagnetic distributionsElectromagnetic wavesArticle10.1364/JOSAB.23.000419