Acoustic resonance spectrometry system and method

An acoustic resonance spectrometry system for analysing a sample (2), the system including:

• an optoacoustic transduction means (1) having an interface (3) in contact with the sample (2) to be analysed,
• an optical pump-probe device (4) adapted to generate a pump beam (14) and a probe beam (15),
• the pump beam (14) being consisted by a series of ultrashort pump light pulses having a repetition frequency (F) located in a spectral domain comprised between several hundreds of megahertz and several tens of gigahertz, optomechanical means for directing the pump beam (14) towards the optoacoustic transduction means (1) for generating a periodic grating of coherent acoustic phonons (200) in the sample (2), the periodic grating of phonons (200) having a pitch (P) determined as a function a ratio (V/F) between the repetition frequency (F) of the pump beam (14) and an acoustic velocity (V) of the coherent acoustic phonons (200) in the sample (2);
• other optomechanical means for directing the probe beam (15) towards the sample (2), so as to form a scattering beam (120) of the probe beam (15) on the periodic grating of coherent acoustic phonons (200),
• a frequency variation device (5) adapted to vary the repetition frequency (F) of the pump beam (14) in a spectral range of said spectral domain, so as to vary the pitch (P) of the grating of coherent acoustic phonons (200) in the sample (5), and
• a photo-detection system (6) configured to receive the scattering beam (120) and to measure a scattering signal as a function of the repetition frequency in said spectral range.