Photoacoustic Pulse Generation in TlGaSe2 Layered Crystals
Keywords:
layered chalcogenides, photoacoustic effect, sound generation.Abstract
Direct time- and space-resolved measurements of laser pulse induced photoacoustic pulses (PAP) in layered TlGaSe2
crystal are presented. It is found that under layer plane excitation PAP can be generated by quite low laser fluences in
contrast to isotropic solid crystals. The PAP amplitude is proportional to laser fluence but it is independent of actual
injected free carrier concentration. The PAP propagates across layers and is multiply reflected from surfaces with small
dispersion with 6 μs decay time. A fine splitting of the PAP is explained by an actual thickness difference due to
crumble off layer planes. Tentative explanation of PAP generation mechanism, which is different from ordinary
thermoelastic process, is presented.
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