December 10, 2006 / Vol. 4, No. 12 / CHINESE OPTICS LETTERS 683
Two-dimensional novel optical lattices with multi-well traps
for cold atoms or molecules
Junfa Lu (
)
1,2
, Xianming Ji (
)
1,3
, and Jianping Yin (
)
1
1
Key Laboratory of Optical and Magnetic Resonance Spectroscopy, Ministry of Education,
Department of Physics, East China Normal University, Shanghai 200062
2
Department of Physics, East China Institute of Technology, Fuzhou 344000
3
Department of Physics, Nantong University, Nantong 226007
Received August 18, 2006
We propose some new schemes to constitute two-dimensional (2D) array of multi-well optical dipole traps
for cold atoms (or molecules) by using an optical system consisting of a binary π-phase grating and a 2D
arra y of rectangle microlens. We calculate the intensity distribution of each optical well in 2D array of
multi-well traps and its geometric parameters and so on. The proposed 2D array of multi-well traps can
b e used to form novel 2D optical lattices with cold atoms (or molecules), and form various novel optical
crystals with cold atoms (or molecules), or to perform quantum computing and quantum information
processing on an atom c hip, ev en to realize an array of all-optical multi-well atomic (or molecular) Bose-
Einstein condensates (BECs) on an all-optical integrated atom (or molecule) c hip.
OCIS codes: 020.7010, 050.1940, 120.5060, 220.2560.
In 1986, the first optical dipole trap for cold Na atoms
with a focused red-detuned Gaussian beam was demon-
strated by Chu et al.
[1]
. After then, people proposed a
va riety of optical dipole traps for cold atoms and suc-
cessfully realized optical trap of neutral atoms. Such as,
Takekoshi et al. in 1995 proposed a new scheme to trap
cold
133
Cs atoms by using a focused CO
2
laser beam
with a giant red-detuning
[2]
. In 1998, Yin et al. pro-
posed a new gravito-optical trap (GOT) scheme to trap
and cool neutral atoms by use of a blue-detuned hol-
low laser bea m (HLB) and the HLB-induced intensity-
gradient cooling
[3]
. In 2001, Birkl et al. proposed some
new optical microtraps and two-dimensional (2D) array
of microtraps for cold atoms on an atom chip
[4]
.Re-
cently, a red-detuned CO
2
or YAG laser is used to real-
ize all-optical atomic Bose-Einstein condensates (BECs),
quantum degenerate Fermi gases, all-optical molecular
BEC, and all-optical output of an atom laser
[5−10]
.
On the other hand, controllable double-well or multi-
well optical traps for cold atoms (or molecules) and novel
optical lattices with a large lattice constant have wide
applications in the field of atom, molecular, and opti-
cal physics, such as the studies of cold collisions between
two atomic or molecular samples
[11]
, matter-wave inter-
ference of trapp ed atoms
[12,13]
, quantum entanglement
between two a ssemble of atoms, and all-optical realiza-
tion of double-well or multi-well BEC and 2D array of
BECs, and so on. In 2004, we proposed a controllable
double-well trap for cold atoms (or cold molecule) and
its 2D array of double-well traps, and studied the rela-
tionships between the characteristic parameters o f each
optical well a nd the parameters of the optical system
[14]
.
In this paper, we report a novel 2D array of control-
lable multi-well traps on a chip, and discuss the potential
applications of our novel optical lattices in the fields of
atom, molecule and quantum optics.
AsshowninFig.1(a),whenaπ-phase plate is extended
along both the x and y directions, a 2D array of π-phase
plates (i.e., a 2D π-phase grating) will be formed. When
a plane light wave with a wavelength of λ goes through
an optical system comp osed of a 2D π-phase grating and
a 2 D array of planar micro-lenses, a 2D array of four-
well optical traps will be formed near the focal plane
of micro-lens array b ecause of the complete destructive-
interference effect at the light axis of each lens, which is
shown in Fig. 1(b).
For a 2D π-phase grating, its amplitude transmission
function is given by
g(x, y)=
(M+1)/2
m=−(M+1)/2
(−1)
m+1
rect
x − (2m −1)a
2a
×
(N+1)/2
n=−(N+1)/2
(−1)
n+1
rect
y − (2n − 1)a
2a
, (1)
where rect(x) or rect(y) is the rectangle function, M
and N are the numbers of micro-lenses in the x and y
directions, respectively. When the center of 2D array of
M ×N micro-lenses is set at the origin (0,0 ) of the x and
y coordinates, the coordinates of the center of mnth lens
Fig. 1. Schematic diagram of a 2D array of four-well optical
traps. (a) Top view of our optical system to generate a 2D
arra y of four-well traps, and (b) intensity-density distribution
of 2D array of four-well optical traps on the focal plane of the
lens array for a =50μm, f = 250 μm, λ =1.06 μm, and the
YAG laser power is p
mn
= 100 mW for each lens.
1671-7694/2006/120683-04 http://www.col.org.cn
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