All-Optical Realization of an Atom Laser

Abstract

We demonstrate an atom laser using all-optical techniques. A Bose-Einstein condensate of rubidium atoms is created by direct evaporative cooling in a quasistatic dipole trap realized with a single, tightly focused CO2-laser beam. An applied magnetic field gradient allows the formation of the condensate in a field-insensitive m(F)=0 spin projection only, which suppresses fluctuations of the chemical potential from stray magnetic fields. A collimated and monoenergetic beam of atoms is extracted from the Bose-Einstein condensate by continuously lowering the dipole trapping potential in a controlled way to form a novel type of atom laser.

Quality factor of a matter-wave beam

“…A spectacular achievement proving the similarity of the atomic and light fields was the realization of a quasicontinuous matter beam analog to a laser [2][3][4][5][6][7][8][9]. It has been shown recently that the extraction of a quasicontinuous atom laser from a Bose-Einstein condensate by a weak RF [10][11][12][13] or Raman [14] outcoupling involves the propagation through a discontinuous potential which degrades the beam collimation.…”

Interference of an array of atom lasers

“…In this way, a comb-like structure of parallel atom laser beams directed downwards is produced. Due to the use of m F = 0 condensates in our all-optical technique, fluctuations of the chemical potential due to stray magnetic fields are suppressed to within the 14 fK/(mG) 2 quadratic Zeeman shift of this clock-state [8].…”

“…On the other hand, light scattering can also imprint an atom phase [12]. Bose-Einstein condensated atoms can be outcoupled from their confining potentials to form atom laser beams [4,5,6,7,8].…”

“…Our experiment is based on the technique of direct generation of Bose-Einstein condensates in optical dipole traps [8,14,15,16]. Initially, cold thermal rubidium atoms ( 87 Rb) are confined in the antinodes of a one-dimensional optical standing wave generated using mid-infrared radiation derived from a CO 2 -laser.…”

“…To date, advances in the field of synthesizing and controlling optical frequencies allow for the measurement and comparison of optical frequencies with radiofrequency precision [2,3]. Atom lasers are coherent atom sources whose outcoupled wave can be seen as a matter wave analog to the radiation emitted by optical lasers [4,5,6,7,8].…”