Fresnel Diffraction Mirror for an Atomic Wave

Abstract

We have experimentally demonstrated a material-independent mirror for atomic waves that uses the Fresnel diffraction at an array of parallel ridges. He* (2 3 S 1 ) and Ne* (1s 3 ) atomic waves were reflected coherently on a silicon plate with a microfabricated grating structure, consisting of narrow wall-like ridges. We measured the reflectivity at grazing incidence as a function of the incident velocity and angle. Our data show that the reflectivity on this type of mirror depends only on the distance between the ridges, the wavelength, and the incident angle, but is insensitive to the material of the grating structure. The reflectivity is observed to increase by 2 orders of magnitude, compared to that of a flat polished silicon surface, where the reflection is caused by the attractive surface potential. For He* atoms, the measured reflectivity exceeds 10% for normal incident velocities below about 25 cm=s.

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“…The quantum reflection of He * atoms on a flat Si surface and on microfabricated surface structures were also investigated (Oberst et al, 2005a(Oberst et al, , 2005b.…”

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“…The magnitude and the distance dependence of these forces were measured in several experiments [5]. In the last few years atom-wall interaction is being studied intensively in connection with the phenomenon of quantum-reflection [6][7][8][9][10][11][12][13]. Theoretical description of atom-wall interaction is given by the Lifshitz theory [1,2,4,5,14] which expresses the van der Waals and Casimir-Polder energy and force through the dynamic electric polarizability of an atom and the frequency-dependent dielectric permittivity of wall material.…”

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“…There normally appear two typical diffraction types, i.e., Fraunhofer diffraction and Fresnel diffraction. The former diffraction, which is also called far-field diffraction, occurs when field waves are passed through an aperture or a slit only causing the size of an observed aperture image to change due to the far-field location of the observation and the increasingly planar nature of the outgoing diffracted waves passing through the aperture; Fresnel diffraction, or near-field diffraction, occurs when a wave passes through an aperture and diffracts in the near field, causing any diffraction pattern observed to differ in size and shape, depending on the distance between the aperture and the projection [38]. When the distance increases, the outgoing diffracted waves become planar, and Fraunhofer diffraction occurs.…”