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Gilman, J.J. Stanton, Richard Heath 2011-07-14T14:16:55Z 2011-07-14T14:16:55Z 10000-01-01 1969 Several aspects of stimulated Brillouin scattering which relate to the determination of acoustic phonon lifetime (Tp) have been investigated. Fused silica was selected as the principal material to be studied because of its optical and acoustic isotropy and its availability in large, optical quality samples. Also, it has the advantage of a distinct dependence of acoustic attenuation on temperature. The main difficulty in using stimulated scattering to determine phonon lifetimes is an uncertainty of whether or not steady-state scattering is achieved during the finite length of the laser pulse. Theoretically, this problem is most acute in solids, where acoustic phonon lifetimes can be of the same order of magnitude as the laser pulse length. This situation was investigated experimentally and it was found that (a) the rise of Brillouin light is much faster than predicted theoretically, and (b) a reasonable fit to steady-state predictions can be obtained when one considers the peak Brillouin power as a function of the laser intensity. Apparently the scattering process adjusts to steady-state conditions in less than 8 nanoseconds rather than in the longer intervals predicted by theory. This conclusion is applied to observed variations in the scattering with temperature, and the corresponding values of Tp are calculated. Similar, though less extensive, studies were conducted using Plexiglas for the scattering medium and essentially the same conclusions were reached. This fact suggests that we are dealing with general properties of stimulated Brillouin scattering and not just anomalous behavior in the specific case of fused silica. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-14T14:16:55Z No. of bitstreams: 1 1969_stanton.pdf: 2429785 bytes, checksum: ab136368c9ffa9ae504b0b3ce2a57539 (MD5) Made available in DSpace on 2011-07-14T14:16:55Z (GMT). No. of bitstreams: 1 1969_stanton.pdf: 2429785 bytes, checksum: ab136368c9ffa9ae504b0b3ce2a57539 (MD5) Previous issue date: 1969 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-14T14:16:55Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:54-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 6074991 http://hdl.handle.net/2142/25805 en 1969 Richard Heath Stanton time dependence temperature dependence stimulated brillouin scattering fused silica acoustic phonon lifetime Time and temperature dependence of stimulated brillouin scattering in fused silica Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.