Rotating a Bose-Einstein condensate using photons with orbital angular momentum

Mikkel Andersen, Pierre Cladé, Changhyun Ryu, Vasant Natarajan, Kristian Helmerson, and William D. Phillips

The transfer of spin (or internal) angular momentum from photons to matter has been well understood and studied for a long time. On the other hand, one can use light fields where the photons also carry orbital angular momentum. The first-order Laguerre-Gaussian field is one such light field where each photon carries one unit of orbital angular momentum along its direction of propagation. We experimentally demonstrate that this quantum of angular momentum can be coherently transferred to sodium atoms in a Bose-Einstein condensate (BEC). The experiment uses a set of counter-propagating Gaussian and Laguerre-Gaussian beams, where an atom in the BEC can absorb a photon from one beam and emit a (stimulated) photon into the other beam. We create different rotational states by choosing different combinations of the light beams. We confirm the coherent transfer of quantized angular momentum by looking at the interference pattern between different rotational states.

Category:  Physics

Guest researcher involved:

Name:                         Pierre Cladé

Mentor's name:            Kristian Helmerson

Division:                       Atomic Physics Division (842)

Laboratory:                  Laser Cooling and Trapping Group

Address:                      Rm. B237, Bldg. 216, Stop 8424

Telephone #:                (301) 975-5231

FAX #:                        301-975-8272

email:                           pierre.clade@nist.gov

            Non Sigma Xi member

Name:                         Mikkel Andersen

Mentor's name:            Kristian Helmerson

Division:                       Atomic Physics Division (842)

Laboratory:                  Laser Cooling and Trapping Group

Address:                      Bldg. 216, Stop 8424

Telephone #:                (301) 975-5913

FAX #:                        301-975-8272

email:                           mikkel.andersen@nist.gov

            Non Sigma Xi member

Name:                         Changhyun Ryu

Mentor's name:            Kristian Helmerson

Division:                       Atomic Physics Division (842)

Laboratory:                  Laser Cooling and Trapping Group

Address:                      Bldg. 216, Stop 8424

Telephone #:                (301) 975-6583

FAX #:                        301-975-8272

email:                           changhyun.ryu@nist.gov

            Non Sigma Xi member