Optical technique for material characterization

1. A method for defining parameters of a polycrystalline material, said method comprising:

illuminating, by a polarized Raman spectrometric apparatus, multiple locations of the polycrystalline material by multiple spots; wherein the polycrystalline material comprises grains;

collecting, by the polarized Raman spectrometric apparatus, radiation emitted from the multiple spots;

generating, by the polarized Raman spectrometric apparatus, a plurality of signals from the multiple locations of the polycrystalline material;

determining, by a computer and based on the plurality of signals, Raman peaks of the multiple locations;

determining, by the computer, and using a peak fitting algorithm, a distribution of Raman amplitudes of the Raman peaks; and

determining, by the computer, an average dimension of the grains based on the distribution of Raman amplitudes of the Raman peaks.

2. The method according to claim 1 , wherein the illumination and the collecting are executed without cross-talk between the multiple spots.

3. The method according to claim 1 , wherein the multiple spots have sub-micron dimensions.

4. The method according to claim 1 , wherein dimensions of the grains are smaller than an optical resolution of the polarized Raman spectrometric apparatus.

5. The method according to claim 1 , comprising adjusting dimensions of the multiple spots by adjusting a numerical aperture (NA) of the polarized Raman spectrometric apparatus.

6. The method according to claim 5 , comprising adjusting the NA using a variable aperture that is positioned at a back-focal-plane of an objective lens of the polarized Raman spectrometric apparatus.

7. The method according to claim 1 , comprising moving the polycrystalline material by a computer-controlled sample stage to facilitate the illumination of the multiple locations.

8. The method according to claim 1 , wherein the illuminating and collecting are executed one location after the other.

9. The method according to claim 1 , wherein the illuminating comprises scanning a spot from one location of the multiple location to another location of the multiple locations.

10. The method according to claim 1 , wherein the determining, by the computer, the average dimension of the grains comprises:

determining a variance of the Raman amplitudes of the Raman peaks;

determining a mean of the Raman amplitudes of the Raman peaks; and

determining the average dimension of the grains by multiplying a dimension of the spot by a ratio between the variance of the Raman amplitudes of the Raman peaks and a square of the mean of the Raman amplitudes of the Raman peaks.

11. The method according to claim 1 , comprising performing a calibration step using a reference polycrystalline material of known grain dimension to determine a mapping between mapping between values of the distribution of Raman amplitudes of Raman peaks to values of the average dimension of the grains.

12. A polarized Raman spectrometric system for defining parameters of a polycrystalline material, the polarized Raman spectrometric system comprising:

a polarized Raman spectrometric apparatus that is configured to:

illuminate multiple locations of the polycrystalline material by multiple spots; wherein the polycrystalline material comprises grains;

collect radiation emitted from the multiple spots; and

generate a plurality of signals from the multiple locations of the polycrystalline material;

a computer that is configured to:

determine, based on the plurality of signals, Raman peaks of the multiple locations;

determine, using a peak fitting algorithm, a distribution of Raman amplitudes of the Raman peaks; and

determine an average dimension of the grains based on the distribution of Raman amplitudes of the Raman peaks.

13. The polarized Raman spectrometric system according to claim 12 , wherein the polarized Raman spectrometric apparatus is configured to illuminate and collect without cross-talk between the multiple spots.

14. The polarized Raman spectrometric system according to claim 12 , wherein the multiple spots have sub-micron dimensions.

15. The polarized Raman spectrometric system according to claim 12 , wherein dimensions of the grains are smaller than an optical resolution of the polarized Raman spectrometric apparatus.

16. The polarized Raman spectrometric system according to claim 2 , wherein the Raman spectrometric apparatus is configured to adjust dimensions of the multiple spots by adjusting a numerical aperture (NA) of the polarized Raman spectrometric apparatus.

17. The polarized Raman spectrometric system according to claim 16 , wherein the Raman spectrometric apparatus is configured to adjust the NA using a variable aperture that is positioned at a back-focal-plane of an objective lens of the polarized Raman spectrometric apparatus.

18. The polarized Raman spectrometric system according to claim 12 , comprising a computer-controlled sample stage that is configured to move the polycrystalline material to facilitate the illumination of the multiple locations.

19. The polarized Raman spectrometric system according to claim 12 , wherein the Raman spectrometric apparatus is configured to illuminate and collect one location after the other.

20. The polarized Raman spectrometric system according to claim 12 , wherein the Raman spectrometric apparatus is configured to scan a spot from one location of the multiple location to another location of the multiple locations.

21. The polarized Raman spectrometric system according to claim 12 , wherein the computer is configured to determine the average dimension of the grains by:

determining a variance of the Raman amplitudes of the Raman peaks;

determining a mean of the Raman amplitudes of the Raman peaks; and

determining the average dimension of the grains by multiplying a dimension of the spot by a ratio between the variance of the Raman amplitudes of the Raman peaks and a square of the mean of the Raman amplitudes of the Raman peaks.

22. The polarized Raman spectrometric system according to claim 12 , comprising performing a calibration step using a reference polycrystalline material of known grain dimension to determine a mapping between mapping between values of the distribution of Raman amplitudes of Raman peaks to values of the average dimension of the grains.