Plasmonic Imaging for Optical Lithography X-ray Wavelengths at Optical Frequencies Experiments: Progress and Plans Yunping Yang Josh Conway Eli Yablonovitch
Feb 23, 2016
Plasmonic Imaging for Optical Lithography
X-ray Wavelengths at Optical Frequencies
Experiments: Progress and Plans
Yunping YangJosh Conway
Eli Yablonovitch
The Problem
Classically the resolution limit is determined by the Rayleigh Criterion:
Various schemes have been developed to push this to finer resolution than the wavelength itself, but the scale will always be set by wavelength
dSin
Constant Energy CurvesBy adiabatically tapering the thin film thickness,
very small (<50nm) plasmon wavelengths are attainable for in plane imaging.
0 20 40 60 80 1000
100
200
300
400 1.5 eV
2.0 eV
2.5 eV
0
100
200
300
20 40
400
60 80
Plas
mon
Wav
elen
gth
in n
m
Silver Film Thickness in nm
Silver Film on Sapphire
t
p
SapphireAg Air
0 0 . 0 2 0 . 0 4 0 . 0 6 0 . 0 8 0 . 1 0 . 1 2 0 . 1 4 0 . 1 6 0 . 1 8 0 . 2 0 . 2 2 0 . 2 4 0 . 2 6 0 . 2 8 0 . 3 0 . 3 2 0 . 3 4 0 . 3 6 0 . 3 8 0 . 4 0 . 4 2 0 . 4 4 0 . 4 6 0 . 4 8 0 . 5 0 . 5 2 0 . 5 4 0 . 5 6 0 . 5 8 0 . 6 0 . 6 2 0 . 6 4W a v e n u m b e r ( r a d / n m )0
0 . 5
1
1 . 5
2
2 . 5
3
3 . 5
4
w(eV)
t=1nm
t=20nm t=5nmt=2nm
0 0.1 0.2 0.3 0.4 0.50
1
2
3
4 200 100 50 20 15 30 40 10
0.6
Plasmon Wavelength in nm
Plasmon Wave-Vector (2/wavelength in nm)
Plas
mon
Ene
rgy
in e
Vh
k
t=thickness of metal film
Optical frequencies, but with X-ray wavelengths!
SapphireAg Air
Dispersion Relation: Constant Thickness Curves
Grating Coupler
Silver
Glass
Grating
• Design and fabricate gratings to maximize the coupling efficiency;• Verify the DR with constant thickness;• Find some material parameters
Launching of Surface Plasmons: ATR Coupler
Optical Setup for ATR Coupler
Laser/2
PBS
BeamExpander
Iris Mirror
Detector Lens LensLens
Lens
4f
4f
SapphireHemisphere
Ag Thin Film
Optical Setup for ATR Coupler
• Characterize thin film, such as roughness, thickness;• Experimentally verify the dispersion relation;• Launching a standing wave for Plasmon Wavelength Measurement
A Possible Solution
This permits X-ray wavelengths at optical frequencies
photoresistsilicon
light h=2.5eV
plas
mon
wav
epl
asm
on w
ave
sapphire plas
mon
wav
e+
++
+-
--
-
sapphire plas
mon
wav
e+
++
+-
--
-
grat
ing
coup
ler
Plasmon Wavelength Measurement
Antonello Nesci, Rene Dandliker, Hans Peter Herzig, “Quantitative amplitude and phase measurement by use of a heterodyne scanning near-field optical microscope,” Optics Letters, Volume 26, Issue 4, 208-210.
Resolution: 1.6 nm
Taper Motivation
dimple lens
out-coupling slot
far-field fromconventional lens
taper
Taper design will be a trade
between absorption
(joule heating),
scattering (an adiabatic
profile), and maintaining a high enough
effective index at all points of
propagation to maintain
features
n9> n8> >n1>n0
Criteria
0 50 100 1500.0
0.1
0.2
0.3
0.4
Loss
/
Wavelength (nm)
It is clear that Loss/ becomes
prohibitively large at
short wavelengths
Thus we change are adiabatic criteria
accordingly
/ = constant
Length (nm)
Silv
er F
ilm T
hick
ness
(nm
)
100 200 300 400 500 600
10
20
30
40
50
60
Taper Profile