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Abstract
Thanks to ultrafast acoustics, a better understanding of acoustic dynamics on a short
time scale has been obtained and new characterization methods at the nanoscale have
been developed. Among the materials that were studied during the development of ultrafast
acoustics, nitride based heterostructures play a particular role due to their piezoelectric
properties and the possibility to generate phonons with over-THz frequency and bandwidth.
Here, we review some of the work performed using this type of structure, with a focus
on THz phonon spectroscopy and nanoscopy. First, we present a brief description of
the theory of coherent acoustic phonon generation by piezoelectric heterostructure.
Then the first experimental observation of coherent acoustic phonon generated by the
absorption of ultrashort light pulses in piezoelectric heterostructures is presented.
From this starting point, we then present some methods developed to realize customizable
phonon generation. Finally we review some more recent applications of these structures,
including imaging with a nanometer resolution, broadband attenuation measurements
with a frequency up to 1THz and phononic bandgap characterization.