ABSTRACT
A. N. Dharamsi and R.P. Joshi; J. Ac. Soc. Am.; 95, 234, 1994
The characteristics of optoacoustic pulses produced by photostrictive means are investigated.Since such pulses have a nonthermal origin,
and can be as short as the inverse of the highest frequency phonons that couple
the photostrictive deformation to the lattice, it is possible to obtain
subpicosecond pulses in this manner. We
discuss the differences between cold photostrictive optoacoustic pulses and
those produced by thermal means in terms of what may be called a risetime
compression factor that characterizes the relative pulsewidths of the thermal
to non-thermal pulses; a criterion for picking materials that would show large
compression factors is given.The
strength of a photostrictive optoacoustic pulse, in the high intensity regime,
is given. Since the non-thermal nature
of the photostrictive pulse is central to the aforementioned compression,
thermalization mechanisms subsequent to laser irradiation of the photostrictive
material are examined.It is shown that
there is a tradeoff between the strength of the compression and the initial
temperature that it exhibits, and an estimate of the expected initial
temperature of the compression is given.The characteristics of photostrictively generated optoacoustic pulses
and those produced by other means, including nonthermal electrostrictive
generation, are compared
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