Abstract
The first results of optical (flourescent) technique application to the study of nonequilibrium terahertz range phonons in noncrystalline solids are reported. 1) The propagation of heat pulses through thin amorphous semiconductor film was studied by phonon detection via phonon-induced effects in exciton luminescence of a crystalline c-Si substrate. The effective frequency down-conversion of THz phonons in a-Si: H films was observed depending on H content. In a-Ge films a time delay in THz phonon pulses propagation was detected which is due to multiple phonon scattering in the films. 2) In Cr3+ -doped bulk oxide glasses the relaxation of optically generated THz phonons was studied by observation of phonon-induced anti-Stokes FLN R-spectra. It was found that fully trapped phonon distribution in the excited glass volume does not thermalize even in a millisecond time scale. The possible role of configurational “softness” and TLS in the observed specific behaviour of THz phonons in amorphous and glassy materials is discussed.
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