Point source in a phononic grating: stop bands give rise to phonon-focusing caustics
We use locally-excited gigahertz surface phonon wavepackets in microscopic line structures of different pitches to reveal profound anisotropy in the radiation pattern of a point source in a grating. Time-domain data obtained by an ultrafast optical imaging technique and by numerical simulations are...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2012-01-01
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| Series: | New Journal of Physics |
| Online Access: | https://doi.org/10.1088/1367-2630/14/12/123015 |
| _version_ | 1797751638369239040 |
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| author | Istvan A Veres Dieter M Profunser Alex A Maznev Arthur G Every Osamu Matsuda Oliver B Wright |
| author_facet | Istvan A Veres Dieter M Profunser Alex A Maznev Arthur G Every Osamu Matsuda Oliver B Wright |
| author_sort | Istvan A Veres |
| collection | DOAJ |
| description | We use locally-excited gigahertz surface phonon wavepackets in microscopic line structures of different pitches to reveal profound anisotropy in the radiation pattern of a point source in a grating. Time-domain data obtained by an ultrafast optical imaging technique and by numerical simulations are Fourier transformed to obtain frequency-filtered real-space acoustic field patterns and k -space phononic band structure. The numerically-obtained k -space images are processed to reveal an intriguing double-horn structure in the lowest-order group-velocity surface, which explains the observed non-propagation sectors bounded by caustics, noted at frequencies above the bottom of the first stop band. We account for these phonon-focusing effects, analogous to collimation effects previously observed in two- and three-dimensional lattices, with a simple analytical model of the band structure based on a plane wave expansion. As the frequency is increased, a transition to dominant waveguiding effects along the lines is also documented. |
| first_indexed | 2024-03-12T16:51:28Z |
| format | Article |
| id | doaj.art-3d57952b22064360b6185a727a8e45d7 |
| institution | Directory Open Access Journal |
| issn | 1367-2630 |
| language | English |
| last_indexed | 2024-03-12T16:51:28Z |
| publishDate | 2012-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | New Journal of Physics |
| spelling | doaj.art-3d57952b22064360b6185a727a8e45d72023-08-08T11:08:57ZengIOP PublishingNew Journal of Physics1367-26302012-01-01141212301510.1088/1367-2630/14/12/123015Point source in a phononic grating: stop bands give rise to phonon-focusing causticsIstvan A Veres0Dieter M Profunser1Alex A Maznev2Arthur G Every3Osamu Matsuda4Oliver B Wright5Department of Electronic and Electrical Engineering, Centre for Ultrasonic Engineering, University of Strathclyde , Glasgow G1 1XW, UKDivision of Applied Physics, Faculty of Engineering, Hokkaido University , Sapporo 060-8628, JapanDepartment of Chemistry, Massachusetts Institute of Technology , Cambridge, MA 02139, USASchool of Physics, University of the Witwatersrand , PO Wits 2050, Johannesburg, South AfricaDivision of Applied Physics, Faculty of Engineering, Hokkaido University , Sapporo 060-8628, JapanDivision of Applied Physics, Faculty of Engineering, Hokkaido University , Sapporo 060-8628, JapanWe use locally-excited gigahertz surface phonon wavepackets in microscopic line structures of different pitches to reveal profound anisotropy in the radiation pattern of a point source in a grating. Time-domain data obtained by an ultrafast optical imaging technique and by numerical simulations are Fourier transformed to obtain frequency-filtered real-space acoustic field patterns and k -space phononic band structure. The numerically-obtained k -space images are processed to reveal an intriguing double-horn structure in the lowest-order group-velocity surface, which explains the observed non-propagation sectors bounded by caustics, noted at frequencies above the bottom of the first stop band. We account for these phonon-focusing effects, analogous to collimation effects previously observed in two- and three-dimensional lattices, with a simple analytical model of the band structure based on a plane wave expansion. As the frequency is increased, a transition to dominant waveguiding effects along the lines is also documented.https://doi.org/10.1088/1367-2630/14/12/123015 |
| spellingShingle | Istvan A Veres Dieter M Profunser Alex A Maznev Arthur G Every Osamu Matsuda Oliver B Wright Point source in a phononic grating: stop bands give rise to phonon-focusing caustics New Journal of Physics |
| title | Point source in a phononic grating: stop bands give rise to phonon-focusing caustics |
| title_full | Point source in a phononic grating: stop bands give rise to phonon-focusing caustics |
| title_fullStr | Point source in a phononic grating: stop bands give rise to phonon-focusing caustics |
| title_full_unstemmed | Point source in a phononic grating: stop bands give rise to phonon-focusing caustics |
| title_short | Point source in a phononic grating: stop bands give rise to phonon-focusing caustics |
| title_sort | point source in a phononic grating stop bands give rise to phonon focusing caustics |
| url | https://doi.org/10.1088/1367-2630/14/12/123015 |
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