Interferometric imaging of surface acoustic waves on a glass sphere

Abstract

We use an ultrafast optical pump and probe technique to investigate the propagation of subgigahertz surface acoustic waves on a 1 mm diameter glass sphere with an aluminum coating. A fiber-based pump setup generates the surface waves and a common-path interferometer images them in the time domain over the sphere surface as they pass through the pole opposite the source of excitation. Fourier analysis allows the acoustic spectrum of the acoustic source to be extracted and waves traveling in opposite directions to be isolated.

Temporal Evolution of Photothermal-Induced Rayleigh Wave and Plate Deformation as an Interference in the Transient Kinetics of Photoinduced Carrier Recombination of a Rutile Titanium Dioxide Single Crystal

“…For a better understanding, the probe deflection signal due to the Rayleigh wave is simulated as described more detail in the Supplemental Material. As a ripple-like surface acoustic wave of axial symmetry, 17–20 the propagation of Rayleigh wave in the radial direction has been simulated. It is deduced from the equation for the linear elastodynamics describing the displacement vector u of an infinitesimal element in an isotropic, homogeneous, and linearly elastic medium: 30,31…”

“…Rayleigh waves include both longitudinal and transverse motions that decrease exponentially in amplitude as the distance from the surface increases, whereas Love waves are horizontally polarized surface waves wherein the particle motion forms only a horizontal line perpendicular to the direction of propagation. The photoinduced Rayleigh wave has been investigated for the past 30 years through probe deflection detection 13–15 in its application to seismological study, e.g., simulating surface waves on the earth's surface, and more recently through an imaging technique called Sagnac interferometry 16–20 to observe the surface wave propagation induced by a laser pulse. In contrast, thermal-induced deformation in metals arising from local thermal expansion caused by the inhomogeneous temperature field after photoexcitation has been studied only since the 1980s; 21–27 mainly, the propagation of longitudinal acoustic phonon and the coherence of longitudinal optical phonon were investigated with observation of the corresponding decay time, being limited only to a temporal range of picoseconds.…”

An integrated method for material properties characterization based on pulsed laser generated surface acoustic waves

“…The experimental technique utilizes a single-longitudinal mode nanosecond laser source for both the generation and recording of the SAWs. It provides nanometer spatial resolution vertical to the film surface, and direct whole-field imaging with nanosecond temporal resolution, thus avoiding extensive surface scanning, as is the case in previous studies [19,20]. Additionally, a theoretical computational approximation simulates the laser-material interaction as well as the generation and propagation of SAWs.…”

Μεθοδολογίες Δυναμικού Νανοσκοπικού Χαρακτηρισμού Υλικών Με Ακουστικές Πηγές Παραγόμενες Από Υπερβραχείς Παλμούς Λέιζερ

“…με την διάδοση των ελαστικών κυμάτων πάνω σε αυτήν. Η τεχνική αυτή προσφέρει το μεγάλο πλεονέκτημα ότι δεν απαιτείται εκτεταμένη σάρωση της υπό μελέτης επιφάνειας, όπως ευρέως συνηθίζεται να γίνεται[41,46], για παράδειγμα στις περιπτώσεις της σημειακής συμβολομετρίας (single ) διάταξη παραγωγής και την ανίχνευσης SAW με πηγή laser ns διάρκειας, (β) διάταξη παραγωγής SAW με πηγή laser fs διάρκειας και ανίχνευσή τους με πηγή ns laser, και (γ) διάταξη συμβολομετρίας λευκού φωτός. Τέλος, δίνονται αναλυτικά οι λεπτομέρειες των διατάξεων αυτοματισμού και ελέγχου που αναπτύχθηκαν, καθώς και αναλυτική παρουσίαση του τρόπου επεξεργασίας και ανάλυσης των καταγεγραμμένων εικόνων (πειραματικών αποτελεσμάτων) με χρήση ειδικά ανεπτυγμένου λογισμικού.…”