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Öğe Finite amplitude pressure field of elliptical and rhomboid transducers in three dimensions(Pleiades Publishing Inc, 2011) Kaya, O. A.; Kaleci, D.; Sahin, A.Design of different type of transducers to enhance image quality by forming narrow beams at the principals of nonlinear acoustics is considered in the paper. Thus, the nonlinear pressure fields of elliptical and rhomboid transducers were simulated in three dimensions. The simulation method presented in this study is based on Aanonsen's model for circular sources, and closely follows the model that recently explored for the nonlinear wave propagation due to square and rectangular sources in three dimensions [Kaya et al. Pressure field of rectangular transducers at finite amplitude in three dimensions, Ultrasound in Med. Biol., vol. 32, no. 2, pp. 271-280, 2006]. It is assumed that elliptical and rhomboid sources are plane sources, and driven at 2.25 MHz fundamental frequency. Typical results of nonlinear acoustical pressure field simulation are presented there in three dimensions for elliptical and rhomboid sources and compared with the results for rectangular source. The similarities and differences between the nonlinear pressure field of rectangular, elliptical and rhomboid sources are discussed. The numerical results show that diffraction effects and acoustical beam cross section depend on the source geometry a lot. It is noticeable that the nonlinear pressure field of a rectangular source has a broader beam profile than elliptical and rhomboid source.Öğe Polarization-Independent Self-Collimated Beam Splitting in Two-Dimensional Photonic Crystals(Ieee Computer Soc, 2012) Yucel, M. B.; Kaya, O. A.; Cicek, A.; Ulug, B.Polarization-independent splitting of self-collimated transverse-electric and transverse-magnetic polarized waves in a two-dimensional square photonic crystal are demonstrated. The beam splitting is facilitated by the existence of sharp edges in flat equifrequency contours.Öğe Self-collimation and slow-sound effect of spoof surface acoustic waves(Amer Inst Physics, 2019) Korozlu, N.; Kaya, O. A.; Cicek, A.; Ulug, B.Self-collimated propagation and slow-sound effect of spoof acoustic surface waves over a thin solid slab with partially embedded spherical cavities in a square lattice are numerically and experimentally demonstrated. Band structure calculations via the Finite-Element Method reveal that a single spoof surface wave band appears below the air-line, which flattens as the spheres are embedded deeper, leveraging the observation of self-collimated slow spoof modes. For a radius-to-lattice constant ratio of 0.45 and embedding depth of 60% of the radius, the surface band is such that non-diffractive guiding of spoof waves along the [11] direction can be achieved. Persistent self-collimated propagation of spoof surface waves over long distances is demonstrated through frequency-domain Finite-Element Method simulations. Plane waves incident from air can couple to the self-collimated modes for a wide range of azimuthal angle of incidence up to 60 degrees, where the polar angle of incidence can be in the range of +/- 15 degrees. Self-collimation of spoof waves is experimentally realized by employing a plane-wave source incident from air. In addition, when the embedding depth is higher than 85%, self-collimated slow spoof modes with group indices higher than 15 can be obtained. The observed phenomena can be utilized in two-dimensional acoustic systems such as logic circuits and interferometric sensing devices. Published under license by AIP Publishing.Öğe Surface modification of YIG by magnet array(Elsevier Science Bv, 2015) Atalay, S.; Kolat, V. S.; Bakir, H. G.; Izgi, T.; Kaya, A. O.; Kaya, O. A.; Gencer, H.In this work, magnetostatic surface spin waves (MSSW) were propagated along the single crystal YIG (Y3Fe5O12) film grown on GGG substrate. In order to obtain magnonic crystals, unlike the conventional methods, the surface of YIG films were magnetically modulated by magnet array in one and two-dimensions. The surface modulated YIG films formed sharp band gaps at approximately 6.55 GHz and 6.58 GHz at 1600 Oe magnetic field for one and two-dimensional magnonic crystals, respectively. It was found that a very small magnetic field change leads a large change in the peak value of band gap frequency. (C) 2015 Elsevier B.V. All rights reserved.Öğe YIG Film for Magnetic Field Sensor(Polish Acad Sciences Inst Physics, 2015) Kaya, A. O.; Atalay, S.; Gencer, H.; Kaya, O. A.; Kolat, V. S.; Izgi, T.Single crystal Y3Fe5O12 (YIG) film was grown onto (111) oriented gadolinium gallium garnet (GGG) substrate by the liquid phase epitaxy (PLD) technique. The X-ray diffraction measurements showed that epitaxial growth of the film along its (111) axis. The surface characteristic was investigated by atomic force microscopy (AFM) measurement. The magnetic field sensor consisted of a rectangular shape with 5 mm wide, 15 mm long and 5 mu m thick YIG film and a pair of identical 50 mu m wide microstrip copper transducers elements separated by 6 mm. The filter was tested by measuring reflection S-11 characteristic at various bias magnetic fields. The results have showed that when the bias field increased from 0 to 2.5 kOe, the frequency value corresponding to S-11 maxima increased from 1 GHz to 9 GHz. This suggests that the wide range magnetic field sensing and the highly sensitive field sensing are simultaneously fulfilled with the YIG film.
