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NIRT: Opto-Plasmonic Nanoscope
NSF NIRT Grant ECS-068863
PIs: Y. Fainman, V. Lomakin, A. Groisman, and G. W. Schmid-Schoenbeim
University of California, San Diego, La Jolla, California 92093-0407
Tel: (858) 534-8909; Fax: (858) 534-1225; E-mail: [email protected]; web site: http://emerald.ucsd.edu
Objective: Plasmonic microscopy with sub-wavelength resolution
SPP Heterodyne Imaging Setup
Nanoscope in Plasmonic Era
Microscope:
Diffraction limited
Diffractive plasmonics:
Fresnel diffraction of SPP
SPP Fresnel Zone Plate
Plasmonic nanoscope:
Sub-diffraction limited
Fresnel Zone Plate
FEM Simulation:
Transmission through Si bumps
SPP Fresnel Zone Plate
Si
Al
rn
CCD Output
.
..
Our focusing approach
Sub-diffraction limited focusing
L. Yin et al, Nano Lett. 5, 1399 (2005)
R. Rokitski et al, Phys. Rev. Lett. 95, 177401 (2005)
R. Rokitski, KA. Tetz, Y. Fainman, PRL, vol.95,
no.17, 21 Oct. 2005, pp.177401/1-4
Time averaged
SPP mode*
l~ 1.5 mm, NIR
(resonant Wood’s anomaly):
kSPP  k//  nK  mK
x
G
y
G
k//  k x  k y  k0  xˆ sin  cos   yˆ sin  sin  
Assuming small modulation (d << a), and
no coupling between adjacent sides:
k1sp 2,23  k0
1,3 2
1,3   2
•
•
•
Al on GaAs
t = 133 fs
t = 266 fs
(-X)
ilspp x
t = 400 fs
O
ik spp
2x
( y  y0 ) 2 )dy0
Measurement
Fresnel Diffraction Calculation
Si-on-Al SPP
Fresnel Zone
Plate
Ultrafast SPP electrodynamics
1.0
1.0
0.9
0.9
0.8
0.8
0.7
0.6
0.5
0.4
0.3
Spatial phase: focused SPP fields
0
y (mm)
0.6
0.5
0.4
0.3
0.2
10
20
30
40
50
0.0
-50 -40 -30 -20 -10
0
10
20
30
40
50
y (mm)
Diffraction theory is valid for SPP
5 μm
Time-resolved SPP focusing
SPP plane wave excitation
Spatial amplitude and phase with converging and diverging illumination
0.7
0.1
0.0
-50 -40 -30 -20 -10
20 μm
How to make sure the incident SPP
wave is planar?
Excitation
Array
Snapshots of amplitude at different time
Image without Fresnel zone plate
Detection
Array
Image with Fresnel zone plate
1 mm
L. Feng, K. Tetz, B. Slutsky, V. Lomakin, Y.
Fainman, Appl. Phys. Lett. 91, 081101 (2007)
Radiative vs. material damping
10
-1
10
I e

SPP
focusing
Focusing
with
Radiation
Loss
Focusing
with
Radiation
Loss
x
 spmat
-100 -100
x
tot
 sp
-2
y (mm)
10
ASE: l = 1520-1570 nm
-100 100
-80
-80
-80
80
-60
-60
-60
60
-40
-40
-40
40
-20
-20
-20
20
0
0
0
y (mm)
I e
0

SPP focusing after the
compensation
of radiation
loss
Focuing
Radiation
Loss
Focusing
withwithout
Radiation
Loss
0
20
20
20
-20
40
40
40
-40
60
60
60
-60
80
80
80
-80
y (mm)
noise limited spectral measurements
Diffractive SPP focusing
y (mm)
polarizers //
to (2,  1)
type modes
R. Rokitski, KA. Tetz, Y. Fainman, Phys. Rev. Lett., vol.95, 2005, pp.177401/1-4
Intensity [a.u.]
a/l0
-3
10
1.03
0
50
1
(-X)

0.3u0 ( y0 ) exp(
Education, Outreach, and Data
Dissemination
Imaging various SPP modes
0.90
exp(ik spp x)
Calculated vs Measured Field
200 mm
2.00
2x
( y  y0 ) 2 )dy0
Field intensity distribution at the focal plane
Holographic lithography
Use of chemically amplified
negative resist (SU-8)
Precise control of fill factor
(easier to make small holes)
Large areas (~ 1 cm2)
1 mm
1.41
ik spp
T

Sample preparation and fabrication
Au on SiO2
200 mm
ilspp x
 u0 ( y0 ) exp(
0.1
• Variety of substrates (GaAs, Si, SiO2, Al2O3)
• Evaporation or sputtering of Al, Au, or Ag metallic films (thickness h ~
50-200 nm)
• ICP-RIE and wet etching (hole diameters d ~ 100-500 nm)
•
f=80mm
exp(ikspp x)
0.2
Sample fabrication: nanoholes in metal films
•
u ( x, y ) 
Optical Signal (a.u.)
t = 0 fs
(planar case)
E-beam direct write
Tailored structures on same
substrate for comparison
Limited area (~ 200 mm)
Fresnel diffraction
4
Spatial amplitude and phaseof scattered SPP field
Normalized frequency (wa/2pc = a/l)
Phase matching condition
Time evolution of SPP wavepacket
2
n2lspp
A SPP Fresnel zone plate was fabricated
at aluminum (Al)/air interface and worked
at the free space wavelength of 1.55 μm
(λspp = 1.547 μm). The designed focal
length was 80 μm.
Time-resolved
SPP interferogram
f=80mm
SPP Bloch modes in 2-D nanohole array
rn  nlspp f 
+1
r3
r2
r1
Input and
reference pulse:
l0 = 1.55 mm
FWHM ~ 200 fs
A 1879 optical microscope
0
Optical Signal (a.u.)
Sample illumination
Power Transmission ~ 0.3
-1
l=1.55mm
(-X)
Fainman Y, Tetz K, Rokitski R, Pang, Optics & Photonics News, vol.17, 24-9, 2006
100
Distance [mm]
1
150
200
1
Simultaneous measurement
tot 
mat  rad
 sp
 sp
 sp
of both planar and corrugated
surface propagation lengths tot
Determines radiative decay  sp  20  5m m  rad  27m m
sp
mat
(coupling strength) from
 sp  80  9m m
grating array
100 100
-100 -100
-50
-50
0
x (mm)
0
50
50100
x (mm)
Measured focal length: 83μm
100
100 -100
-100 -100
-50
-50
0
0
50
x (mm) x (mm)
50 100
100
Designed focal length: 80μm
High intensity focused SPP field is observed
L. Feng, K. Tetz, B. Slutsky, V. Lomakin, Y. Fainman, Appl. Phys. Lett. 91, 081101 (2007)
• Established new graduate courses: Nanophotonics (ECE 242A)
and Optics in Space and Time (ECE 240B)
• Modified Undergraduate Photonics Laboratory in Engineering,
Physics and Biochemnistry (opt. comm., CGH, and NLO)
• Graduate students weekly meetings and seminars on recent
progress and other relevant topics in nanophotonics
• Involvement of undergraduate students via NSF’s REU program
• Establishing education and outreach projects with the UCSD’s
Preuss School, designed for 6-12 grades student coming from
disadvantaged households [e. g., Ph.D. students are serving as
mentors and leaders of robotics club; RET program with the
Undergraduate Photonics Laboratory in Engineering]
• Saperstein-2005 JSOE Woolley Fellow, 2006 Summer Graduate
Teaching Fellow
• Numerous journal publications, conference presentations
including invited conference papers
• http://emerald.ucsd.edu