Centre National De La Recherche Scientifique

Bruker Nano Gmbh

Université Paris-Saclay

Alexandre Dazzi

Honghua Yang

Anirban Roy

A system for measuring the absorption of a laser radiation by a sample is provided. The system comprises: &#x2022;(i) a pulsed laser source, suitable for emitting pulses at a repetition frequency fand arranged so as to illuminate the sample; &#x2022;(ii) an AFM probe arranged so as to be able to be placed in contact with the region of the surface of the sample on one side, the AFM probe having a mechanical resonance mode at a frequency f; and &#x2022;(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, characterized in that it also comprises a translation system designed to displace the sample at a frequency f.

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

A method for obtaining optical spectroscopic information about a sub-micron region of a sample with quantitatively controlled depth/volume of the sample subsurface using a scanning probe microscope. With controlled probing depth/volume, the method can separate top surface data from subsurface optical/chemical information. The method can also be applied in liquid suitable for studying biological and chemical samples in their native aqueous environments, as opposed to air. In the method, a depth-controlled spectrum of the surface layer is constructed by illuminating the sample with a beam of infrared radiation and measuring a probe response using at least one of the resonant frequencies of the probe. The surface sensitivity is obtained by limiting the heat diffusion effect of the subsurface so as to confine the signal. The signal confinement is achieved through non-linearity of the acoustic wave with probe, as well as benefits gained by a high modulation frequency of the infrared radiation source at &#x3e;1 MHz.

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Orsay, France

Alexandre Dazzi