Download - Micro-diffractive nanostructures for cold-atom manipulation (and other interesting stuff)
Micro-diffractive nanostructures for cold-atom manipulation
(and other interesting stuff)Groupe optique atomique et applications aux nanostructures
Université Paul Sabatier—CNRSToulouse, France
http://www.nanocold.cict.fr http://www.fastnet.fr
FRISNO-8Ein-Bokek, Israel
February 20-25, 2005
The basic idea
incoming laser light
output optical field
structured surface
cold atoms
Subwavelength StructuresFIB Fabrication
Arrays of Holes in Metal Films
Light transmission spectrum
Is this evidence of surface plasmons?
Decorated Slits and Holesin Subwavelength Ag
Membranes
Light transmission througha slit flanked by periodic
groovesdetected far-field transmission
calculated profile
Garcia-Vidal, et al., Appl. Phys. Lett. 83, 4500 (2003)
Measuring the transmission profile–atomic fluorescence mapping of the
field intensity
Relation between atomic fluorescence and field intensityexcited atoms field intensity
100 nm slit flanked by 10 grooves each side
measured
calculated
How does the slit/groove structureproduce the observed field
distributions?
Composite Diffracted Evanescent Wave
Lezec and ThioOptics Express, 12 3629 (2004)
Composite Evanescent Wave-I
Consider diffraction at a slit of width d. The field along x is given by:
00 0( , 0) Si Si
2 2E d dE x z k x k x
0
sin( )Si( )l tl dtt
Kowarz, Appl. Optics. 34, 3055 (1995)
-2 -1 1 2
-1.5
-1
-0.5
0.5
1
1.5
--2 -1 1 2
-1.5
-1
-0.5
0.5
1
1.5
= -4 -2 2 4
-2
-1.5
-1
-0.5
0.5
1
1.5
2
Composite Evanescent Wave-II
The phase shift of pi/2 isa signature of the CEW.0
0( ) cos2
E dE x k xx
-4 -2 2 4
-2
-1.5
-1
-0.5
0.5
1
1.5
2
x/d
CEWs launched on the surface
incoming laser light
output optical field
structured surface
A pi/2 phase shift between the directly transmitted wave and the
CEW
100 nm830 nm
50 nm
variablejog
incoming light
We can “jog” the structures tocompensate for the phase shift
00( ) cos
2E dE x k xx
Jogged and unjogged slit structures
unjogged jogged inward by ¼ period
Distribution and number of grooves controls the output optical field
far-field intensity, no phase shift
far-field intensity, with phase shift
We can produce a “phased array” with constructive interference in
the forward direction. The result is a forward “flame” .
Flame divergence vs. grooves—expmt. and model for unjogged grooves
10 grooves
30 grooves
calculation
Flame intensity vs. groove number for jogged and unjogged grooves
unjogged jogged
Flame angular distributions
incoming light
outgoing light
coupling
f
CCDmicroscopeobjective
d
/d f
Angular distribution of light vs. groove-slit spacing (in units of period N) for 5
grooves
Emission diagram (expanded)0°
-6°
3° -3°
6°
N = 1 (0.83 µm shift) N = 6 (4.98 µm shift) N = 24 (19.92 µm shift)
Intensity angular distribution—jogged grooves output side, 3 selected distances
Emission diagram (expanded)0°
-6°
3° -3°
6°
N = 1 (0.83 µm shift) N = 6 (4.98 µm shift) N = 24 (19.92 µm shift)
-1 -0.5 0.5 1
0.5
1
1.5
2
2.5
3
CDEW model measured
Intensity angular distribution—output side, unjogged red, jogged black
Emission diagram (expanded)N = 16 for both types of devices
0°
-6°
3° -3°
6°
-2 -1 1 2
1
2
3
4
CDEW model:Phase shift: CDEW/2
Index: nCDEW=850/830=1.024Relative field amplitude x=2/x
Angular lobe spacing
0 5 10 15 20 25
1
2
3
4
5
6
7
8
9
Grooves Shift (µm)
Subs
eque
nt lo
bes
spac
ing
(deg
rees
)
jogged
unjogged
CDEW model
0,5
1,5
2,5
3,5
4,5
5,5
6,5
7,5
8,5
9,5
0 5 10 15 20 25
Experiment
Next step: mirror MOT to get cold atoms close to surface
Next step: mirror MOT with the optical funnel generated by a planar
nanostructured phased arrayMirror MOT
atom trajectories
phased arraystructure
optical funnel
plane waveexcitation
Toward integrated structures:cold atom sources and transport
on a chip
Interaction atomes neutres-lumière
Champs proches optiques : confinement sub-longueur
d’onde de la lumière.
nanolithographie optique atomique
cohérente : diffraction
interaction dipolaire
Diffraction and confinement
Coupled resonant rings:symmetric/antisymmetric modes
Funnel effect: optical potential above the rings
f
e0
0ik
iErk
rE
Proposé et réalisé : J.V. Hajnal & G.I Opat (1989).Théorie : R. Deutschmann (1993), C. Henkel (1994).Expérience : Villetaneuse (1996), Orsay (1998).
surfk
*surfksurfk
surfk surfk2
)2cos(1),( 020 xkeVzxV surf
z
Réseau à onde évanescente stationnaire
surfk2surfk2
+1-1
ikiE
Réseau à onde évanescente nanostructurée :
xm Lm eQ 2
x
nm300L
période orientation motif
20
22 kmm k m
izm
mm eez lkElE ),(
Diffraction de l’onde évanescente :
A. Roberts & J.E. Murphy (1996)
msurfm Qkk
Autre approche : potentiel nanostructuré
D. van Labeke & D. Barchiesi
Periodicity controllable through angle of optical coupling-1
50 nm above surface 250 nm above surface
Periodicity controllable through angle of optical coupling-2
50 nm above surface 250 nm above surface
dB=5nmLx=Ly=250nmdiff=20mrade100nm=40°=55°
n=2.1 (TiO2)zr=250nm
MOT
Experimental parameters
Tales from the future—nanophotonics, addressable atom manipulation with optical arrays
E=10V/200nm E= 0.5 108 V/m
BaTiO3: n0=2.4 r42=1300pm/V
n=0.45 (20%)
SrRu4O3
BaTiO3
Quartz
Electro-Optic Beaming Controlwith variable index of refraction
AgV
Variable Depth Focusing
SrRu4O3
BaTiO3
Quartz
Electro-Optic Beaming Control
AgV
Steering
Change n from 0.8 to 1.2
Future: arrays of optical traps loaded with one or more atoms
125µm
R. Dumke, et al. PRL 89, 097903 (2002)
Summary—evolution of conception
Yesterday: Today:
10 µm
Tomorrow:
The GroupGuillaume Gay Renaud Mathevet
Bruno Viaris
Olivier Alloschery
Colm O’Dwyer
Gaetan Leveque