Acoustic resonance spectrometry system and method

Patent metadata

Field	Value
Publication number	US-10578555-B2
Application number	US-201716318845-A
Country	US
Kind code	B2
Filing date	Jul 19, 2017
Priority date	Jul 20, 2016
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

Disclosed is an acoustic resonance spectrometry system for analysing a sample, which includes an optical pump-probe device adapted to generate a pump beam and a probe beam, the pump beam being consisted of a series of ultra-short pump light pulses having a repetition frequency in the spectral domain of the gigahertz, the pump beam being directed towards an optoacoustic transducer to generate a periodic grating of coherent acoustic phonons in the sample, the probe beam being directed towards the sample to form a scattering beam of the probe beam on the grating of phonons, a frequency variation device being adapted to vary the repetition frequency of the pump beam in a spectral range and a photo-detection system configured to measure a scattering signal as a function of the repetition frequency in the spectral range.

First claim

The invention claimed is:

1. 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.

2. The system according to claim 1 , wherein the optical pump-probe device ( 4 ) comprises a laser ( 40 ) configured to emit a monochromatic continuous laser beam ( 140 ), a variable frequency microwave generator configured to generate a control signal at said repetition frequency and a plurality of electro-optical modulators ( 41 , 42 , 43 , 44 ) configured to receive the control signal and to modulate the monochromatic continuous laser beam in amplitude and in phase at said repetition frequency and a compressor ( 46 ) configured to receive the laser beam modulated in amplitude and in phase at said repetition frequency and to generate the pump beam ( 14 ), the pump beam ( 14 ) having a spectral distribution comprising a plurality of discrete wavelengths separated by a free spectral interval determined by the repetition frequency.

3. The system according to claim 2 , wherein the probe beam is temporally continuous.

4. The system according to claim 2 , wherein the probe beam is consisted by another series of ultra-short light pulses.

5. The system according to claim 2 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is different from the pump wavelength.

6. The system according to claim 2 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is equal to the pump wavelength.

7. The system according to claim 1 wherein the probe beam ( 15 ) is temporally continuous.

8. The system according to claim 7 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is different from the pump wavelength.

9. The system according to claim 7 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is equal to the pump wavelength.

10. The system according to claim 1 , wherein the probe beam ( 15 ) is consisted by another series of ultra-short light pulses.

11. The system according to claim 10 , wherein the probe beam ( 15 ) is consisted of a portion of the pump beam ( 14 ).

12. The system according to claim 10 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is different from the pump wavelength.

13. The system according to claim 10 , wherein the pump beam having a pump wavelength, the probe beam having a probe wavelength, the probe wavelength is equal to the pump wavelength.

14. The system according to claim 1 , wherein the pump beam ( 14 ) having a pump wavelength, the probe beam ( 15 ) having a probe wavelength, the probe wavelength is different from the pump wavelength.

15. The system according to claim 14 , wherein the probe beam is consisted of a portion of the pump beam.

16. The system according to claim 1 , wherein the pump beam ( 14 ) having a pump wavelength, the probe beam ( 15 ) having a probe wavelength, the probe wavelength is equal to the pump wavelength.

17. The system according to claim 16 , wherein the probe beam is consisted of a portion of the pump beam.

18. The system according to claim 1 , wherein the pump beam ( 14 ) and the probe beam ( 15 ) are in normal incidence on the sample, or wherein the pump beam ( 14 ) is in normal incidence on the sample and the probe beam ( 15 ) in oblique incidence on the sample, or wherein the pump beam ( 14 ) is in oblique incidence on the sample and the probe beam ( 15 ) in normal incidence on the sample, or wherein the pump beam ( 14 ) is in oblique incidence on the sample and the probe beam ( 15 ) has another oblique incidence on the sample.

19. The system according to claim 1 , wherein the probe beam ( 15 ) is configured to illuminate an area of the sample ( 2 ) and wherein the photo-detection system ( 6 ) includes a two dimensionally-resolved image detector and an optical system configured to form an image of said sample area on the image detector.

20. An acoustic resonance spectrometry method, the method comprising the following steps:
generating a pump beam ( 14 ) consisted by a series of ultra-short pump light pulses having a repetition frequency (F) located in a spectral domain comprised between several hundreds of megahertz and several tens of gigahertz,
the pump beam ( 14 ) being incident on an optoacoustic transduction means ( 1 ) having an interface ( 3 ) with a sample ( 2 ) to be analysed, so as to generate 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 of 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 ),
generating a probe beam ( 15 ), the probe beam ( 15 ) being directed towards the sample ( 2 ) so as to form a scattering beam ( 120 ) by scattering of the probe beam ( 15 ) on the periodic grating of coherent acoustic phonons ( 200 ),
varying the repetition frequency (F) of the pump beam ( 14 ) in a spectral range so as to vary the pitch (P) of the periodic grating of coherent acoustic phonons ( 200 ) in the sample ( 5 ),
photo-detecting the scattering beam ( 120 ) as a function of the repetition frequency (F) in said spectral range, and
measuring a scattering signal as a function of the repetition frequency (F) in said spectral range.

Assignees

• Univ Bordeaux
• Inst Polytechnique Bordeaux
• Centre Nationale De La Recherche Scient
• Ecole Nat Superieure Des Arts Et Metiers
• Commissariat Energie Atomique
• Inst Doptique Graduate School

Inventors

• Audoin Bertrand
• Cormier Eric
• Lhermite Jérôme
• Santarelli Giorgio
• Guillet Yannick
• Aubourg Adrien

Classifications

• H01S3/0014

  Monitoring arrangements not otherwise provided for (photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003) · CPC title

• G01J3/2823

  Imaging spectrometer · CPC title

• G01N2021/638

  Brillouin effect, e.g. stimulated Brillouin effect · CPC title

• G01J3/4412

  Scattering spectrometry (particle sizing by light scattering G01N15/0205; optical velocimetry of particles G01P5/20, G01P5/26) · CPC title

• G01J2009/006

  using pulses for physical measurements · CPC title