Point source in a phononic grating: stop bands give rise to phonon-focusing caustics
Name
Veres-2012-Point source in a phononic grating.pdf
Size
2.75 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Maznev, Alexei
Veres, Istvan A.
Profunser, Dieter M.
Every, Arthur G.
Matsuda, Osamu
Wright, Oliver B.
Date Issued
December 2012
Journal
New Journal of Physics
Publisher
IOP Publishing
Citation
Veres, Istvan A. et al. “Point Source in a Phononic Grating: Stop Bands Give Rise to Phonon-focusing Caustics.” New Journal of Physics 14.12 (2012): 123015.
Version
Final published version
Abstract
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.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike 3.0
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1088/1367-2630/14/12/123015
