Atoms can be pushed, pulled, and trapped using laser beams. The light imparts an optical force on the atom that can be utilized to manipulate its position. Now researchers have demonstrated a new kind of atom-acting optical force that squeezes a whole cloud of atoms. Such a collective force could give rise to a cloud that traps itself, or it could allow researchers to modify the density distribution of the cloud in such a way that it focuses other laser beams.
Under the right conditions, a laser photon colliding with an atom transfers its momentum to the atom. Bombard the atom with photons of exactly the right energy, and the atom’s position can be directly controlled. Similarly, lasers can be used to create an electric field that varies in intensity across space. Single atoms that interact with this field feel a force pulling them toward the field’s lowest-energy point. The optical force demonstrated by Noam Matzliah and colleagues from the Weizmann Institute of Science, Israel, acts differently.
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