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Super-Diffraction Limited Wide FieldImaging and Microfabrication
Based on Plasmonics
Peter T. C. So, Yang-Hyo Kim, Euiheon Chung,Wai Teng Tang, Xihua Wang, ErramilliShyamsunder, Colin J. R. Sheppard
MIT, Boston University, National University of Singapore
2
Overview• Background
– Total internal reflection
• Motivation
• Theory
– Surface Plasmon and Photon coupling
• Experimental Setup
• Experiment & Results
• Future work
3
Total internal reflection (TIR)
(http://qbx6.ltu.edu)
x
z−~ zk z
zE e
[ ]ω= + −0 exp ( )x zE E i k x k z t
4
ω ω− − −= +
= +
2( ) ( )
2
( )
2 [1 cos(2 )]
i kx t i kx tI x Ee Ee
E kx
Uniform excitation Standing wave excitation
ω−= =2( ) 2( ) i kx tI x Ee E
x
z
k
High n
(Chung et al., Opt. Lett., 2006)
ω φ ω
φ
− − − −= +
= + −
2( ) ( )
2
( )
2 [1 cos(2 )]
i kx t i kx tI x Ee Ee
E kx
TIR imaging
5
TIR lithography
π θλ
=2 sinnk
λ θ= /(2 sin )p n
(Ecoffet et al., Adv. Mater., 1998)
= +2( ) 2 [1 cos(2 )]I x E kx
Photosensitive materialx
z
x
z
p: period of the pattern, n: refractive index
p
6
Motivation
Total internal reflection (TIR) of light
Imaging Lithography
Interference of Two Evanescent WavesSurface Plasmon Resonance (SPR)
Strong field enhancement
⇒High S/N ratio
Shorter Wavelength⇒Higher Resolution
7
metal
air
20 ~ 200!!output
input
EE
=
Eoutput
x
z−~ zk z
zE e
---+++ ---+++ ---+++ ---+++ ---+++ ---+++ ---++
glass0θEinput
Field enhancement by SPR
(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
8
0 0( ) sin ( 2 / )sp photon xk k mg g acωε θ π= = + =
spk
( )photon xk 1ε metal
2ε air
glass
k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant
Higher resolution by SPR (I)
0ε
0θa
9
Higher resolution by SPR (II)
1/ 21 2
1 2
0 0
( / 2 )
( ) sin
ω π
ε εωε ε
ωε θ
= ==
⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪
= +⎪⎩
h h
h
surface plasmon
photon x
E hp k
kc
k mgc
TIR +Grating
+TIR gratingkTIRk
ωlight line TIR
xk
k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
0k
532 nm 104 nm !!
10
Experimental setup
11
SPR field enhancement experiment (I)
SiOx (5nm)
Glass (n=1.522)
Fluorescent beads (d = 40nm)SPR angle (~45°)Incident power (7.8 mW)N = 48 samples
SPR sample TIR sample
Bead
Au (40 nm)
12
SPR field enhancement experiment (II)
(a) SPR (P pol) (b) SPR (S pol)
(c) TIR (P pol) (d) TIR (S pol)
12㎛
12㎛
Intensity (A.U.)
13
SPR field enhancement experiment (III)Intensity from 48 beads
SPR(P pol) SPR(S pol) TIR(P pol) TIR(S pol)
Inte
nstiy
(A.U
.)
0
100
200
300
400
500
P-value<0.001
14
TIR Lithography experiment (I)
Spin coating Congo Red solution with deionized waterExposure (800 mW/cm2 S-polarization for 30 min)Exposure (2000 mW/cm2 P-polarization for 10 min)
S-polarization P-polarization
Congo Red (n=1.9)
(Ohdaira, Y., et al., Colloids Surf. A, 2006)
Glass (n=1.522)
150 1.00 2.00㎛
0
1.00
2.00㎛
(Ohdaira, Y., et al.,Colloids Surf. A, 2006)
(a) S-polarization (b) P-polarization
(Kim, Y., et al., In preparation)
TIR Lithography experiment (II)
16
Summary
Interference of two surface plasmon waves for imaging and lithography.
1) Strong field enhancement (high S/N ratio)2) Longer wave vector (higher resolution)
The results:1) SPR strong field enhancement (bead imaging)2) P-polarization Congo Red lithography is possible.
17
Future Work
• Make a corrugated gold coated glass sample• The high resolution (~50 nm) imaging and
lithography with the sample
18
Thank you !
&
Questions ?
19
Future Work (II)
~80 nm~200 nm
(Maier, Plasmonics: Fundamentals and Applications. 2007, Springer)
20
0 0.1 0.2 0.3 0.4 0.5 0.60
0.1
0.2
0.3
0.4
0.5
0.6
0.7
kx (108/m)
W (1
015H
z)
SP dispersion relation of glass-Au-air
Surface plasmonlight lineTIRTIR+grating
Future Work (II)
508 nm 105 nm473 nm excitation
Air
Au
Glass
138 nm
21
0 0.1 0.2 0.3 0.4 0.5 0.60
0.1
0.2
0.3
0.4
0.5
0.6
0.7
kx (108/m)
W (1
015H
z)
SP dispersion relation of glass-Au-Congo Red
Surface plasmonlight lineTIRTIR+grating
Future Work (II)
Congo Red
Au
Glass
130 nm
513 nm 104 nm532 nm excitation
22
Resolution I
x
( ) ( )NA61.0
NA4.0 λλ
<=∆r
( ) ( )⎟⎟⎠⎞
⎜⎜⎝
⎛−′+⎟⎟
⎠
⎞⎜⎜⎝
⎛+′
NA2.0~
NA2.0~ λλ xhxh
(MIT 2.710 Optics lecture note)
23
Resolution II
• Rayleigh resolution criterion (imaging)
• Optical Projection Lithography resolution
λ λθ
=0.61 0.61sinNA n
λ λκ κθ
=1 1 sinNA n
θ
Numerical ApertureNA= n sin θ
Objective lens
Κ1: constant for a specific lithographic process
(Chiu at al., IBM Journal of Research and Development, 1997. 41)
Polarization
S-polarization P-polarization
Ei
kiBi
Interface
Er kr
Br
Et
ktBt
Ei
kiBi
Interface
Erkr
Br
Et
ktBt
http://www.monos.leidenuniv.nl/smo
25
Linear polarizer
(Collett, Edward. Field Guide to Polarization, SPIE Field Guides vol. FG05, SPIE (2005))
26
Surface Plasmon-Coupled Emission
(E. Chung, thesis, MIT, 2007)
27
AFM
• Deflection of the cantilever is measured.
• Feedback mechanism prevent the collision of the tip and the surface.
Humphris at al., A mechanical microscope: High-speed atomic force microscopy,
Applied Physics Letters 86, 034106 (2005).
28
Piezoelectric effect
-
+
-
+
+
-
+
-
(+)
(-)A pushing force:
(aka: compression)A pulling force:(aka: tension)
(+)(-)
(http://www.ndt-ed.org/)
The unit cell of crystal silicon dioxide deformation
+
-
+
-
29
Fluorescence
(http://www.probes.com/)
30
Congo Red
(Ohdaira, Y., et al., Colloids Surf. A, 2006)(http://en.wikipedia.org/wiki/Azobenzene)
31
Spin coating
Centrifugal force spread a fluid resin.
32
CCD & CMOS
Uniform image quality
High fill factor
Low noise
Simple
Cost less
Consume less power
Many function
Integration on one chip
33
t-testPopulation
µσ
Mean: Standard deviation:
Mean: Standard deviation: Number of samples:
XSn
Sample
µ−=
/XTS n
µ≠P value : the provability that when random sampling
X
µsmall P value : we can trust as with higher probability.
X
34
Original experimental setup
35
Fringe spacing
( )2 TBx = f / sinM n θ
11
2 1
1p(x )=2 M
TBf ff x
λ⎛ ⎞⎛ ⎞⎜ ⎟⎜ ⎟
⎝ ⎠⎝ ⎠
p= sin2nλ θ
(E. Chung, thesis, MIT, 2007)
36
SPR field enhancement experiment (IV)
(E. Chung, thesis, MIT, 2007)
37
Surface plasmon and photon coupling (I)
1/ 21
0 0
2
1 2
( ) sin
ε εε
ωε θ
ωε
⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪
=⎪⎩
surface plasmon
photon x
kc
kc
k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
TIRk
ωlight line
TIR
'xk
0k
Grating
gratingk
ωlight line
'xk
0k1/ 2
1 2
1 2
0 0( ) sin
ε εωε ε
ωε θ
⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨⎪
= +⎪⎩
surface plasmon
photon x mk g
kc
c
38
Surface plasmon and photon coupling (II)
11/
2
0 0
1
2
2
( ) sin
ε εε
ωε θ
εω⎧ ⎛ ⎞⎪ = ⎜ ⎟⎪ +⎝ ⎠⎨
⎪=⎪⎩
surface plasmon
photon x
kc
kc
k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
TIRk
ωlight line
TIR
'xk
0k
39
Wave vector change by grating
0
(sin sin )2 2( ) ( ) (sin sin )
m i
out x in x m i
AB CD a mmk k k m mga a
θ θ λ
π λ πθ θλ
− = − =
⎛ ⎞− = − = = =⎜ ⎟⎝ ⎠
(Hecht, OPTICS, 2001, Addison Wesley)
A D
B Cθi θm
a
40
Wavelength dependence of various materials
(Hecht, Optics. 2002, Addison-Wesley)
41
Dispersion in atom
(Hecht, Optics. 2002, Addison-Wesley)
42
Dispersion relation of SP (I)
(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
43
Dispersion relation of SP (II)
(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
44
Dispersion relation of SP (III)
(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
45
Dielectric function of gold
(Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer)
Source of Noise in Optical Detectors
(1) Optical shot noise (Ns) –inherent noise in counting a finite number of photons per unit time
(2) Dark current noise (Nd) –thermally induced “firing” of the detector
(3) Johnson noise (NJ) –thermally induced current fluctuation in the load resistor
Since the noises are uncorrelated, the different sources of noise add in quadrature
2222JdS NNNN ++∝
(MIT 2.710 Optics lecture note)