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Fakultät Physik

Introduction to ultrafast acoustics

Ultrafast acoustics is everything about acoustic waves of ultrahigh frequencies in solids (or acoustic phonons in quantum representation).  “Ultrahigh” means the frequencies ranging from tens of GHz to several THz. Such acoustic waves are referred to as hypersound.

Like its low-frequency counterparts,  hypersound is a powerful tool for for both fundamental and applied research at the nanoscale:

  • studying the elastic properties of nanostructures with sizes down to monoatomic scale,
  • visualizing internal morphology with nanometer resolution,
  • dynamically controlling the optical processes via ultrafast modulation of optical and electronic resonances,
  • manipulating collective spin excitations in magnetic materials (like ferro- or antiferromagnets),
  • carrying and processing information in nonconventional computing. 

Following this diversity of potential applications and variety of physical effects, our research ranges from detecting acoustic pulses with unrivaled sensitivity to developing phonon-based neuromorphic hardware concepts.

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Acoustic frequency ranges: The frequencies of ultrafast acoustics are in the GHz-THz (hypersonic) frequency range, which is well above the frequencies exploited in everyday applications. The nanometer wavelength, which overlaps with the wavelength of visible light, frequency matching with collective magnetic excitations, and unique versatility make hypersonic acoustic waves extremely attractive for various nanoscale applications.

Research tools

Ultrashort laser pulses are the exclusive tool for excitation and time-resolved detection of hypersound acoustic waves. So, we operate with a wide range of tools for ultrafast optical spectroscopy, including tunable femtosecond oscillators (lasers) combined with mechanical delay lines or asynchronous optical sampling (ASOPS) controllers, streak cameras, lock-in amplifiers spectrometers, ultrafast photoreceivers, and single-photon counters.