Time and temperature dependence of stimulated brillouin scattering in fused silica

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Stanton, Richard Heath

Contributors dc:contributor

• Gilman, J.J.

• time dependence
• temperature dependence
• stimulated brillouin scattering
• fused silica
• acoustic phonon lifetime

Statement dc:rights

• 1969 Richard Heath Stanton

Language dc:language

en

Identifier

6074991

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25805