Browsing by Author "Sigalas, M. M."
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Item Open Access Exceptionally directional sources with photonic-bandgap crystals(Optical Society of America, 2001-11) Biswas, R.; Özbay, Ekmel; Temelkuran, B.; Bayındır, Mehmet; Sigalas, M. M.; Ho, K.-M.Three-dimensional photonic-bandgap crystals are used to design and fabricate uniquely directional sources and receivers. By utilizing the resonances of a Fabry-Perot cavity formed with photonic-bandgap crystals, we were able to create exceptionally directional sources by placing the sources within such a cavity. Very good agreement between finite-difference time-domain calculations and the experiment is obtained. Radiation patterns with half-power beam widths of less than 12 degrees were obtained. (C) 2001 Optical Society of America.Item Open Access Experimental demonstration of highly confined photonic crystal based waveguides(IEEE, 2001) Bayındır, Mehmet; Özbay, Ekmel; Temelkuran, B.; Sigalas, M. M.; Soukoulis, C. M.; Biswas, R.; Ho, K. M.The bending and guiding of the electromagnetic (EM) waves in highly confined waveguides was demonstrated. The electromagnetic waves were constructed by removing a single rod from a perfect three layer-by-layer photonic crystals. A layer-by-layer dielectric photonic crystal based on square shaped alumina rods was used with center-to-center separation of 1.12 cm. The results suggested the use of the layer-by-layer photonic crystal structure in the design of optoelectronic integrated circuits.Item Open Access Guiding, bending, and splitting of electromagnetic waves in highly confined photonic crystal waveguides(American Physical Society, 2001) Bayındır, Mehmet; Özbay, Ekmel; Temelkuran, B.; Sigalas, M. M.; Soukoulis, C. M.; Biswas, R.; Ho, K. M.We have experimentally demonstrated the guiding, bending, and splitting of electromagnetic (EM) waves in highly confined waveguides built around three-dimensional layer-by-layer photonic crystals by removing a single rod. Full transmission of the EM waves was observed for straight and bended waveguides. We also investigated the power splitter structures in which the input EM power could be efficiently divided into the output waveguide ports. The experimental results, dispersion relation and photon lifetime, were analyzed with a theory based on the tight-binding photon picture. Our results provide an important tool for designing photonic crystal based optoelectronic components.Item Open Access Highly directional resonant antennas built around photonic crystals(IEEE, 1999) Özbay, Ekmel; Temelkuran, Burak; Bayındır, Mehmet; Biswas, R.; Sigalas, M. M.; Tuttle, G.; Ho, K. M.We report a photonic crystal-based resonant antenna with a very high directivity and gain. The layer-by-layer dielectric photonic crystal we used in our experiments was designed to have a three dimensional band gap with a mid-gap frequency around 12 GHz. We used the output port of a microwave network analyzer and a monopole antenna to obtain EM waves. The input port of the network analyzer and a standard gain horn antenna were used to receive the radiated EM field from the monopole antenna. The receiver was kept free to rotate around the antenna. We investigated the radiation characteristics of this monopole antenna, which was inserted into the planar defect structures built around a photonic crystal that consisted of 20 layers. The planar defect was formed by separating the 8th and 9th layers of the structure. In order to suppress the radiation in the backward direction, we intentionally chose one of the mirrors of the cavity to have a higher reflectivity (/spl sim/18-20 dB) than the front mirror.Item Open Access Highly doped silicon micromachined photonic crystals(IEEE, Piscataway, NJ, United States, 2000) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Kavanaugh, J. P.; Sigalas, M. M.; Tuttle, G.Summary form only given. Photonic crystals are periodic structures with the property of reflecting the electromagnetic (EM) waves in all directions within a certain frequency range. These structures can be used to control and manipulate the behaviour of EM waves. Although earlier work concentrated on building these crystals with dielectric materials, there are certain advantages of introducing metals to photonic crystals. First, metals offer a high rejection rate when compared to the dielectric crystals. Second, for microwave applications, the dimensions of metallic crystals can be kept much smaller than the minimum dimensions needed for a typical dielectric crystal. In the paper, we propose a method for the fabrication of layer-by-layer metallic photonic crystals. A similar method had been used by Ozbay et al. to fabricate dielectric photonic crystals using silicon wafers. We fabricated a new layer-by-layer photonic crystal using highly doped silicon wafers.Item Open Access Microwave applications of photonic band gap structures(IEEE, 2000-10) Temelkuran, Burak; Bayındır, Mehmet; Özbay, Ekmel; Biswas, R.; Sigalas, M. M.; Tuttle, G.; Ho, K.-M.We have investigated two major applications of photonic band gap materials. We demonstrated the guiding and bending of electromagnetic waves through planar waveguides built around layer-by-layer photonic crystals. We then investigated the radiation properties of an antenna that was formed by a hybrid combination of a monopole radiation source and a cavity built around the same photonic crystal structure. © 2000 IEEE.Item Open Access Photonic crystal-based resonant antenna with a very high directivity(American Institute of Physics, 2000-09-24) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Biswas, R.; Sigalas, M. M.; Tuttle, G.; Ho, K. M.We investigate the radiation properties of an antenna that was formed by a hybrid combination of a monopole radiation source and a cavity built around a dielectric layer-by-layer three-dimensional photonic crystal. We measured a maximum directivity of 310, and a power enhancement of 180 at the resonant frequency of the cavity. We observed that the antenna has a narrow bandwidth determined by the cavity, where the resonant frequency can be tuned within the band gap of the photonic crystal. The measured radiation patterns agree well with our theoretical results. (C) 2000 American Institute of PhysicsItem Open Access Quasimetallic silicon micromachined photonic crystals(American Institute of Physics, 2001) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Kavanaugh, J. P.; Sigalas, M. M.; Tuttle, G.We report on fabrication of a layer-by-layer photonic crystal using highly doped silicon wafers processed by semiconductor micromachining techniques. The crystals, built using (100) silicon wafers, resulted in an upper stop band edge at 100 GHz. The transmission and defect characteristics of these structures were found to be analogous to metallic photonic crystals. We also investigated the effect of doping concentration on the defect characteristics. The experimental results agree well with predictions of the transfer matrix method simulations. (C) 2001 American Institute of Physics.