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Optical digital tomographic microscopy can be used for profilometry. The profile of the surface can be estimated from measurements of the complex diffracted far field obtained when the sample is illuminated successively under various incidences. This estimation is done with an inversion procedure based on a rigorous model of diffraction. Then we can reconstruct objects with strong slopes and high permittivity contrasts which shows that this procedure is potentially an interesting alternative to classical optical profilometry based on Mirau, Linnik, or Michelson interferometers.

In this web page we present a brief overview of our research in optical diffraction tomography. For more details on each topic have a look at the references.

The figure on the right side shows that a resolution far beyond that of conventional far-field optical profilometers can be reached experimentally with optical diffraction tomography. This result is obtained in the presence of multiple scattering when using an adapted inverse scattering algorithm for profile reconstruction.

The reference profile given by scanning electron microsocpy is plotted in (a) and (b) in solid line. (a) Reconstruction given by Kirchhoff-Fraunhofer method (dot dashed line) and Zygo profilometer (dotted line). (b) Reconstruction given by Newton-Kantorovitch algorithm (dashed line) and AFM (dot dashed line).

The resolution of this new profilometry technique (optical diffraction tomography) is comparable to that of atomic force microscopes.

Reference :

  • S. Arhab, G. Soriano, Y. Ruan, G. Maire, A. Talneau, D. Sentenac, P. C. Chaumet, K. Belkebir and H. Giovannini,Nanometric resolution with far-field optical profilometry, Phys. Rev. Lett. 111, 053902 (2013). pdf