We develop a versatile theoretical approach to the study of ultracold atom diffractive scattering from light-field gratings by combining calculations of the optical near field generated by evanescent waves close to the surface of periodic nanostructured arrays with atom wavepacket propagation techniques. Nanometric one dimensional (1D) and 2D arrays with subwavelength periodicity deposited on a transparent surface and optically coupled to an evanescent wave source exhibit intensity and polarization gradients on the length scale of the object and can produce strong near-field periodic modulation in the optical potential above the structure. As a specific and experimentally practical example we calculate the diffraction of cold Cs atoms dropped onto a periodic optical potential crafted from a 2D nanostructure array. For an “out-of-plane” configuration we calculate a wide diffraction angle (≃2°) and about 60% of the initial atom flux in diffraction orders ±1, an encouraging result for future experiments.
DOI:10.1103/PhysRevA.65.053615
Voir en ligne : Phys. Rev. A 65, 053615 (2002)