Abstract

We demonstrate a method for increasing the amount of power available for laser cooling applications by using a multimode optical fiber. Through randomization of phase shifts of modes within the fiber on time scales faster than the center-of-mass response time of the atoms, a smooth time-averaged trapping beam is generated. The principle has been demonstrated in a pyramidal magneto-optical trap. The method is particularly suitable for the harnessing of the high output power of broad-area diode lasers for laser cooling.

© 2005 Optical Society of America

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References

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  1. A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
    [CrossRef]
  2. C. S. Adams and E. Riis, "Laser cooling and trapping of neutral atoms," Prog. Quantum Electron. 21, 1-79 (1997).
    [CrossRef]
  3. C. E. Wieman and L. Hollberg, "Using diode lasers for atomic physics," Rev. Sci. Instrum. 62, 1-6 (1991).
    [CrossRef]
  4. I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
    [CrossRef]
  5. E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
    [CrossRef] [PubMed]
  6. K. I. Lee, J. A. Kim, H. R. Noh, and W. Jhe, "Single-beam atom trap in a pyramidal and conical hollow mirror," Opt. Lett. 21, 1177-1179 (1996).
    [CrossRef] [PubMed]

2000

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
[CrossRef]

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

1997

C. S. Adams and E. Riis, "Laser cooling and trapping of neutral atoms," Prog. Quantum Electron. 21, 1-79 (1997).
[CrossRef]

1996

1991

C. E. Wieman and L. Hollberg, "Using diode lasers for atomic physics," Rev. Sci. Instrum. 62, 1-6 (1991).
[CrossRef]

1987

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Adams , C. S.

C. S. Adams and E. Riis, "Laser cooling and trapping of neutral atoms," Prog. Quantum Electron. 21, 1-79 (1997).
[CrossRef]

Andalkar, A.

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
[CrossRef]

Cable, A.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Chu, S.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Dieckmann, K.

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

Hollberg, L.

C. E. Wieman and L. Hollberg, "Using diode lasers for atomic physics," Rev. Sci. Instrum. 62, 1-6 (1991).
[CrossRef]

Jhe, W.

Kim, J. A.

Lamoreaux, S. K.

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
[CrossRef]

Lee, K. I.

Noh, H. R.

Prentiss, M.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Pritchard, D. E.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Raab, E. L.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Riis, E.

C. S. Adams and E. Riis, "Laser cooling and trapping of neutral atoms," Prog. Quantum Electron. 21, 1-79 (1997).
[CrossRef]

Shvarchuck, I.

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

Walraven, J. T. M.

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

Warrington, R. B.

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
[CrossRef]

Wieman , C. E.

C. E. Wieman and L. Hollberg, "Using diode lasers for atomic physics," Rev. Sci. Instrum. 62, 1-6 (1991).
[CrossRef]

Zielonkowski, M.

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

Appl. Phys. B

I. Shvarchuck, K. Dieckmann, M. Zielonkowski, and J. T. M. Walraven, "Broad-area diode-laser system for a rubidium Bose-Einstein condensation experiment," Appl. Phys. B 71, 475-480 (2000).
[CrossRef]

Opt. Lett.

Phys. Rev. Lett.

E. L. Raab, M. Prentiss, A. Cable, S. Chu, and D. E. Pritchard, "Trapping of neutral sodium atoms with radiation pressure," Phys. Rev. Lett. 59, 2631-2634 (1987).
[CrossRef] [PubMed]

Prog. Quantum Electron.

C. S. Adams and E. Riis, "Laser cooling and trapping of neutral atoms," Prog. Quantum Electron. 21, 1-79 (1997).
[CrossRef]

Rev. Sci. Instrum.

C. E. Wieman and L. Hollberg, "Using diode lasers for atomic physics," Rev. Sci. Instrum. 62, 1-6 (1991).
[CrossRef]

A. Andalkar, S. K. Lamoreaux, and R. B. Warrington, "Improved external cavity design for cesium D1 (894 nm) diode laser," Rev. Sci. Instrum. 71, 4029-4031 (2000).
[CrossRef]

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Figures (4)

Fig. 1
Fig. 1

Experimental setup. The MOT laser beam is passed through an optical isolator and coupled into a multimode fiber. The speckle pattern in the multimode fiber output is randomized with a piezoelectric actuator. The fiber output beam is circularly polarized and used for a pyramidal MOT. A repumper beam recovers Rb atoms otherwise lost from the cycling transition.

Fig. 2
Fig. 2

These images demonstrate (a)–(c) the correlation between MOT fluorescence and (d)–(f) the contrast in the corresponding time-averaged speckle pattern. The speckle patterns are displayed on identical linear scales, with black corresponding to zero intensity. The atom populations N and piezo drive parameters are indicated. The MOT images show a total area of 1.5 mm×1.1 mm to scale, while the speckle patterns show a 4.7 mm×4.7 mm cross section. The lines in some of the speckle patterns are due to interference in the CCD camera.

Fig. 3
Fig. 3

Contrast and MOT population as a function of the piezo driving parameters. (a) Typical radial autocorrelation function S of a speckle pattern. The extracted quantities Smax and Smin are used to calculate the speckle contrast C=(Smax-Smin)/Smax. (b) Linear grayscale representation of the contrast C versus driving voltage and frequency. Contrast values C>0.12 (black) correspond to speckle patterns with nearly 100% intensity modulation. (c) MOT population N versus driving voltage and frequency by use of the indicated linear grayscale representation.

Fig. 4
Fig. 4

MOT population N versus speckle contrast C for two experiments with different fiber modulators. The curves drawn through the data represent the general trends. The insets show the MOT populations represented as in Fig. 3(c). The data points inside the ellipse in panel (b) correspond to the “overdriving” region (as indicated by an arrow). The population measurements have statistical uncertainties of ±3×105 in panel (a) and ±5×104 in panel (b).

Equations (4)

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τ2ϕmcωΓ1/2,
E=nEn(t)exp{i[kn·x-ωt+δn(t)]},
N=4πΔΩ 2|e|ηPDΓΔIPD,
S2D(Δr)=AimageI(r-Δr)I(r)dr,

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