Nonlinear Photoacoustics

Our group has developed a novel platform for generating large amplitude bulk and surface acoustic waves in solids, without optical damage to the substrate, up to the mechanical failure threshold. Successive cylindrically focused excitation pulses are spatially shifted on the substrate such that the thermoelastic response launched by each pulse matches the velocity of a particular wave, resulting in a boost of its amplitude. Significant in-plane strain amplitudes (> 1 %) can be achieved in that manner, and since the pulse energy is distributed over a wide area, laser-induced damage can be mitigated. This approach is naturally suitable to strain engineering of two-dimensional materials and thin films, among others.

 

 

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