Nanometric resolution with far-field optical profilometry.

We show experimentally that a resolution far beyond that of conventional far-field optical profilometers can be reached with optical diffraction tomography. This result is obtained in the presence of multiple scattering when using an adapted inverse scattering algorithm for profile reconstruction. This new profilometry technique, whose resolution can be compared to that of atomic microscopes, also gives access to the permittivity of the surface.

Full polarization optical profilometry.

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. Outside the validity domain of perturbative theories of diffraction, the profile is determined by using an iterative inverse wave scattering numerical method. In this paper we show that, for perfectly conducting surfaces, the two fundamental polarization cases involve different distances of interaction in the multiple scattering phenomenon. The use of both polarization cases in the inversion process leads to a considerable improvement of the lateral resolution. Robustness to noise is also discussed.

Full wave optical profilometry.

We show that tomographic diffractive microscopy can be used for profilometry applications with high transverse resolution. We present an iterative reconstruction procedure, based on a rigorous wave scattering model, that permits us to retrieve the profile of rough metallic interfaces from the complex scattered field. The transversal resolution is subwavelength, and can even fall below the classical resolution limit if the profile is rough enough for multiple interactions to occur. Large profiles, with tens of wavelength size, can be investigated.