Evanescent Wave Atomic Mirror

• Main Authors: Ghezali, S, Taleb, A
• Format: Conference Proceeding
• Language: English
• ISSN: 0094-243X
• DOI: 10.1063/1.2999923

A research project at the 'Laboratoire d'electronique quantique' consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition d = oL-o0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the mueV) is less than the maximum of the dipolar potential barrier [O2/D where O is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of l0/2p where l0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of l0/2p. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely proportional to the detuning d and is responsible of the non specular aspect of the atomic reflection (atomic diffusion). In the contrary, we note that the specularity of the reflection preserve the coherence of the atomic wave packet. The atoms will constitute a probe of the rugosity of the prism surface which can be imperfect or super-polished.