Diffraction of an atom laser in the Raman-Nath regime

An atom interferometer is a ubiquitous tool for measuring fundamental constants and inertial sensing. While it has been extremely useful in measuring inertial rotations, the fine-structure constant, gravity gradients, and local gravity, the measurement process lacks the ability to probe continuously due to its single-shot nature. In this work, we experimentally demonstrate the diffraction of an atom laser in the Raman-Nath regime, a key step towards the development of an atom-laser-based interferometer. The diffraction orders can be precisely controlled, and momenta up to +/- 18hk can be imparted to the atom laser. We form the "atom laser" by outcoupling a quasicontinuous beam of coherent atoms from a reservoir of Rb-87 Bose-Einstein condensate lasting up to 400 ms. This atom laser then interacts with a grating formed by a standing wave of far-detuned laser light. By controlling the interaction time, the strength of diffraction into various orders can be controlled. Such diffraction would allow for the construction of an atom-interferometer to probe changes in physical environments continuously up to a few hundred milliseconds.