Dresden 2006 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.130: Poster

Donnerstag, 30. März 2006, 16:00–18:00, P1

Coherent phonon avalanches in ruby — •L. G. Tilstra, A. F. M. Arts, and H. W. de Wijn — Debye Institute, Department of Physics and Astronomy, Utrecht University, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands

Coherent phonons are generated by stimulated emission in a single crystal of dilute ruby at 1.4 K, and subsequently seen to propagate through the crystal. The “hot” medium is the metastable E(²E) doublet split in a magnetic field, whose levels are connected by a one-phonon transition. The doublet is population inverted by pulsed selective optical excitation into its upper level, and the ensuing stimulated phonon emission is detected via the accelerated growth of the lower level’s population by the use of luminescence. The coherence is established by comparison with the predictions from a set of Bloch equations [1] designed to describe a strain wave coupled to a nonequilibrium spin system.

For longer crystals, in which the hot zone has a limited extent, the crystal surfaces act as mirrors, and the generated phonon beam passes repeatedly through the hot zone, much like in an optical laser. The phonon beam is amplified upon each pass until the population inversion becomes exhausted. Both the divergence and the frequency spread of the beam have been studied.

[1] L. G. Tilstra, A. F. M. Arts, and H. W. de Wijn, Phys. Rev. B 68, 144302 (2003).