Showing papers by "Irfan Bulu published in 2004"

Enhanced transmission of microwave radiation in one-dimensional metallic gratings with subwavelength aperture

Abstract: We report a theoretical and experimental demonstration of enhanced microwave transmission through subwavelength apertures in metallic structures with double-sided gratings. Three different types of aluminum gratings (sinusoidal, symmetric rectangular, and asymmetric rectangular shaped) are designed and analyzed. Our samples have a periodicity of 16mm, and a slit width of 2mm. Transmission measurements are taken in the 10–37.5GHz frequency spectrum, which corresponds to 8–30mm wavelength region. All three structures display significantly enhanced transmission around surface plasmon resonance frequencies. The experimental results agree well with finite-difference-time-domain based theoretical simulations. Asymmetric rectangular grating structure exhibits the best results with ∼50% transmission at 20.7mm, enhancement factor of ∼25, and ±4° angular divergence.

Physics and applications of photonic crystals

Abstract: Photonic crystals are three-dimensional periodic structures having the property of reflecting the electromagnetic (EM) waves in all directions, for a certain range of frequencies. Defects or cavities around the same geometry can also be built by means of adding or removing material. The EM fields in such cavities are usually enhanced, and by placing active devices in such cavities, one can make the device benefit from the wavelength selectivity and large enhancement of the resonant EM field within the cavity. In this work, we have demonstrated the resonant cavity enhanced (RCE) effect by placing microwave detectors in defect structures built around dielectric based photonic crystals. A power enhancement factor of 3450 was measured for planar cavity structures. The tuning bandwidth of the RCE detector extends from 10.5 to 12.8 GHz. We also used these defect structures to demonstrate waveguiding around layer-by-layer photonic crystals. An air gap introduced between two photonic crystal walls was used as waveguide. We observed full transmission of the EM waves through these planar waveguide structures within the frequency range of the photonic band gap. The dispersion relations obtained from the experiments were in good agreement with the predictions of our waveguide model. We also observed 35% transmission for the EM waves traveling through a sharp bend in an L-shaped waveguide carved inside the photonic crystal.