Towards Atom Interferometry with Atoms Around an Optical Nanofiber

Light-pulse atom interferometry was invented in the 1990s and it has become a precise tool to measure inertial forces and test fundamental laws of physics. Using laser-cooled atoms as the coherence source and photon-atom momentum transfer to split and combine matter waves, atom interferometers have applications in mobile gravimeters and inertial sensors. As their sensitivity scales with the light-atom interaction time, compact atom interferometers usually require a physical size from a few centimeters to a meter to allow the atoms to free-fall. On-chip atom interferometers have not yet been reported. Here, we propose a new type of atom interferometer using an evanescent field from an optical nanofiber. Because the waist of the optical nanofiber is thinner than the laser wavelength, the optical nanofiber will not only guide the laser beam but also produce a tight-confinement evanescent field. We will first use a two-color optical lattice from the evanescent field to trap the atom above the nanofiber, and then create the atomic superpositions by Bloch oscillation with a moving optical lattice. Recently, we have successfully fabricated optical nanofibers by tapering regular single-mode fibers to a waist diameter of 250 nm and waist length of 1 mm with a laser transmission of over 99%. The next step is to install the fabricated nanofiber in the center of a single-beam MOT for the interferometer signal detection. In the future, we plan to realize the atom interference with an on-fiber manipulation.