title: Phononic crystal surface mode coupling and its use in acoustic Doppler velocimetry.
abstract: It is numerically shown that surface modes of two-dimensional phononic crystals, which are Bloch modes bound to the interface between the phononic crystal and the surrounding host, can couple back and forth between the surfaces in a length scale determined by the separation of two surfaces and frequency. Supercell band structure computations through the finite-element method reveal that the surface band of an isolated surface splits into two bands which support either symmetric or antisymmetric hybrid modes. When the surface separation is 3.5 times the lattice constant, a coupling length varying between 30 and 48 periods can be obtained which first increases linearly with frequency and, then, decreases rapidly. In the linear regime, variation of coupling length can be used as a means of measuring speeds of objects on the order of 0.1m/s by incorporating the Doppler shift. Speed sensitivity can be improved by increasing surface separation at the cost of larger device sizes.
authors.affiliation: Department of Physics, Faculty of Arts and Science, Mehmet Akif Ersoy University, 15030 Burdur, Turkey; Department of Electrical Engineering, Jack Baskin School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA. Electronic address: ahmetcicek@mehmetakif.edu.tr.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Cicek
authors.affiliation: Naval Architecture and Marine Engineering Programme, Faculty of Engineering, Piri Reis University, 34940 Istanbul, Turkey. Electronic address: asalman@pirireis.edu.tr.
authors.forename: Aysevil
authors.initials: A
authors.lastname: Salman
authors.affiliation: Department of Computer Education and Educational Technology, Faculty of Education, Inonu University, 44280 Malatya, Turkey. Electronic address: oademkaya@inonu.edu.tr.
authors.forename: Olgun Adem
authors.initials: OA
authors.lastname: Kaya
authors.affiliation: Department of Physics, Faculty of Science, Akdeniz University, 07058 Antalya, Turkey. Electronic address: bulug@akdeniz.edu.tr.
authors.forename: Bulent
authors.initials: B
authors.lastname: Ulug
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D018608:Ultrasonography, Doppler / Q000295:instrumentation*
keywords: Doppler shift; Finite-element method; Phononic crystal; Surface modes