Surface plasmon-based detection for picosecond ultrasonics in planar gold-dielectric layer geometries

Acoustic Wave Generation in Nanofluids: Effect of the Kapitza Resistance on the Thermophone to Mechanophone Generation Mechanism Transition

“…This is due to the fact that the source term q in the last line of eq is spatially homogeneous , ultimately resulting in a spatially homogeneous mechanical excitation of the film. We remark that, for thicker films, the heating can be inhomogeneous, and so this behavior can be significantly altered . Also the purely thermophone case presents downward peaks at the same odd n frequencies, despite the nanofilm thermal expansion being zero in this case.…”

“…We remark that, for thicker films, the heating can be inhomogeneous, and so this behavior can be significantly altered. 95 Also the purely thermophone case presents downward peaks at the same odd n frequencies, despite the nanofilm thermal expansion being zero in this case. This is due to the expansion and compression of water which, in the thermophone effect, pushes against the nanofilm activating its eigenfrequencies, specularly to what happens during the mechanophone effect.…”

Vibrational Anharmonicity and Energy Relaxation in Nanoscale Acoustic Resonators

“…13 Long lived vibrational modes were observed, even though there was no special preparation of the substrate. The nanoplate also displayed up to n = 7 overtone modes, see also ref 14, with frequencies that were almost exact integer multiples of the fundamental breathing mode frequency. 13 The lifetimes of the overtone modes were significantly smaller than that of the fundamental.…”

“…Conversely, when the acoustic impedance of the substrate is larger than that of the nanoplate, the frequencies are the same as those for an isolated nanoplate with mixed boundary conditions (see the Supporting Information for more details). For a supported nanoplate the quality factors of the vibrational modes depend sensitively on the difference in acoustic impendence ( Z = ρc l ) between the nanoplate and the substrate, with larger quality factors obtained for large Δ Z . , It is also important to note that in general only the odd order modes are observed in transient absorption experiments on nanoplates, , as these are the ones that correspond to volume changes …”

“…For a supported nanoplate the quality factors of the vibrational modes depend sensitively on the difference in acoustic impendence (Z = ρc l ) between the nanoplate and the substrate, with larger quality factors obtained for large ΔZ. 16,20 It is also important to note that in general only the odd order modes are observed in transient absorption experiments on nanoplates, 13,14 as these are the ones that correspond to volume changes. 23 Figure 1 shows vibrational spectra of two nanoplates on a glass coverslip obtained by Fourier transformation of the transient absorption microscopy traces.…”