The Atomic Fabry-Perot Interferometer

Abstract

Since the realisation in 1995 of an atomic Bose-Einstein condensate (BEC), atom optics has began to take advantage of the remarkable properties of such a coherent matter wave: indeed, the large number of atoms sharing the same quantum state can be described as a classical C-number matter wave. The relation of the atomic field of a BEC to a non-degenerate thermal cloud is analogous to that of a laser field to the light of a lamp. In the last few years, a great effort has been focussed on the extraction of coherent atom laser beams from trapped BECs and, very recently, on the study of nonlinear atom optical effects, for which the classical wave character of the atom laser pulses plays a fundamental role. The atomic analog of the nonlinear susceptibility of optical media is given by atom-atom interactions: the two-body elastic collisions are in fact responsible for a nonlinear cubic term in the equations of motion for the atomic field which has the same form as a Kerr-like nonlinear refractive index. A few different nonlinear atom optical effects have already been studied by several authors, e.g. atomic four-wave mixing and gap-solitons. Our present contribution is a proposal of a new concept of Fabry-Perot interferometer for atomic matter waves to be used for cavity atom optics. The physical importance of such a device is obvious: indeed, not only it can effectively filter the atoms in terms of their velocity, but also it can