System for measuring the absorption of a laser emission by a sample

A system for measuring the absorption of a laser radiation by a sample with a nanometric or subnanometric spatial resolution comprising:

• (i) a pulsed laser source, suitable for emitting pulses at a tunable wavelength and at a repetition frequency fl and arranged so as to illuminate a portion of the sample so as to induce a thermal expansion of a region of the surface of the sample;
• (ii) an AFM probe comprising a beam bearing an AFM tip oriented in a so-called vertical direction and arranged so as to be able to be placed in contact with the region of the surface of the sample in which a thermal expansion is induced on one side and held mechanically on another side, the AFM probe having a mechanical resonance mode at a frequency fm;
• and
• (iii) a detector configured to measure the amplitude of the oscillations of the AFM probe resulting from the absorption of the laser radiation by the region of the surface of the sample,
• wherein the system further comprises a piezoelectric translation system designed to displace the sample in said vertical direction, the displacement being modulated at a frequency fp, and in that the detector is configured to measure the amplitude of a frequency component fm, of the oscillations of the AFM probe, the frequency fp being chosen so as to generate oscillations of the AFM probe at the frequency fm by a mix of acoustic waves.