Opto-Acoustics & Laser Ultrasound

Research in opto-acoustics aims to introduce innovative methods for the generation and detection of acoustic waves by lasers for the acoustic evaluation and non-destructive testing of materials and structures.

Here, the role played by the piezoelectric transducer in traditional ultrasonic measurements is attributed to a laser, but the latter can play this role remotely and without any contact with the materials. If necessary, the excitation and detection of sound can be very local (down to the micron scale, diameter of the focused laser beam) or, on the contrary, can quickly and optically scan large areas (up to a few meters).

Opto-acoustics, in addition to other frequency ranges accessible by traditional methods, gives access to hypersonic frequencies of acoustic waves (above 1 GHz). In particular, acoustic waves with frequencies above 10 GHz have wavelengths shorter than the micrometer in solids. This makes laser-generated and detected hypersonic sound a unique tool for the non-destructive evaluation of nanocrystalline materials and nanostructures, as well as for three-dimensional imaging inside continuously inhomogeneous media with nanometers scale axial resolution.

The non-contact nature of this technique makes it particularly suitable for the evaluation of materials in hostile environments, such as very high temperatures and/or very high pressures, making it a very interesting control tool for both fundamental research and industrial applications.