Guided atom laser

A trapped cloud of atoms chilled into a Bose–Einstein condensate is a single coherent structure. When extracted from the trap and allowed to propagate, it acts like a laser beam, except that the coherent waves are of matter rather than light. In a typical atom laser, the atoms are released and accelerated by gravity, a process that decreases the atom laser’s de Broglie wavelength. Now, physicists from the Institut d’Optique Graduate School in Palaiseau, France, have coupled atoms from an optomagnetic BEC trap to a horizontal optical waveguide, which generated a quasi-continuous atom laser, impervious to gravity and having a constant de Broglie wavelength of 0.5 μm. The RF coupling converts the atoms from a magnetic to a nonmagnetic state, and they emerge with a typical velocity of 9 mm/s and a velocity spread of just a few μm/s, driven along a confining beam of light, as shown in the figure. Changing the RF coupler’s frequency can tune the de Broglie wavelength, and changing its power can alter the atom laser’s density. In addition, the researchers showed that the coupling is 100% efficient; no atoms are lost during extraction and transport along a 1-mm guide. The new atom laser opens promising prospects for applications in atom interferometry and more fundamental studies of matter-wave propagation. (W. Guerin et al., Phys. Rev. Lett. 97 , 200402, 2006 .)