NIRT: Opto-Plasmonic NanoscopeNIRT: Opto-Plasmonic NanoscopeNSF NIRT Grant ECS-068863

PIs: Y. Fainman, V. Lomakin, A. Groisman, and G. W. Schmid-Schoenbeim

University of California, San Diego, La Jolla, California 92093-0407Tel: (858) 534-8909; Fax: (858) 534-1225; E-mail: fainman@ece.ucsd.edu; web site: http://emerald.ucsd.edu

Microscope: Diffraction limited

Nanoscope in Plasmonic Era

Plasmonic nanoscope: Sub-diffraction limited

A 1879 optical microscope

Our focusing approachSub-diffraction limited focusingR. Rokitski et al, Phys. Rev. Lett. 95, 177401 (2005)

L. Yin et al, Nano Lett. 5, 1399 (2005)

Objective: Plasmonic microscopy with sub-wavelength resolutionObjective: Plasmonic microscopy with sub-wavelength resolution

//x y

SPP G Gn m k k K K

// 0ˆ ˆsin cos sin sinx y k k k k x y

1,3 21 2,2 3 0

1,3 2

sp k

k

Assuming small modulation (d << a), and no coupling between adjacent sides:

Phase matching condition (resonant Wood’s anomaly):

(planar case) (-X)

Norm

aliz

ed

fre

qu

en

cy (

a/2

c =

a/

) ~ 1.5 m, NIR

SPP Bloch modes in 2-D nanohole array

Sample fabrication: nanoholes in metal films• 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)

200 m

Al on GaAs

1 m

E-beam direct write• Tailored structures on same

substrate for comparison• Limited area (~ 200 m)

E-beam direct write• Tailored structures on same

substrate for comparison• Limited area (~ 200 m)

200 m

Au on SiO2

1 m

Holographic lithography• Use of chemically amplified

negative resist (SU-8) • Precise control of fill factor

(easier to make small holes)• Large areas (~ 1 cm2)

Holographic lithography• Use of chemically amplified

negative resist (SU-8) • Precise control of fill factor

(easier to make small holes)• Large areas (~ 1 cm2)

SPP Heterodyne Imaging Setup

Time averaged SPP mode*

Time-resolved SPP interferogram

Input and reference pulse:0 = 1.55 mFWHM ~ 200 fs

CCD OutputSample illumination

R. Rokitski, KA. Tetz, Y. Fainman, PRL, vol.95, no.17, 21 Oct. 2005, pp.177401/1-4

Time evolution of SPP wavepacketSpatial amplitude and phaseof scattered SPP field

= 0 fs = 133 fs = 266 fs = 400 fs

Ultrafast SPP electrodynamics

Spatial phase: focused SPP fieldsSpatial amplitude and phase with converging and diverging illumination

R. Rokitski, KA. Tetz, Y. Fainman, Phys. Rev. Lett., vol.95, 2005, pp.177401/1-4

1 1 1tot mat radsp sp sp

20 5totsp m

80 9matsp m

27radsp m

Radiative vs. material damping

0 50 100 150 20010

-3

10-2

10-1

100

Distance [m]

Inte

nsity

[a.

u.]

totsp

x

I e

matsp

x

I e

Simultaneous measurement of both planar and corrugated surface propagation lengthsDetermines radiative decay (coupling strength) from grating array

Diffractive plasmonics: SPP Fresnel Zone Plate

Diffractive plasmonics: SPP Fresnel Zone Plate

2 2

4spp

n spp

nr n f

SPP Fresnel Zone Plate

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.

Fresnel Zone Plate

Al

Si

Sample preparation and fabricationSample preparation and fabrication

Si-on-Al SPP

Fresnel Zone Plate

Si-on-Al SPP

Fresnel Zone Plate

20 μm 5 μm

SPP plane wave excitationSPP plane wave excitation

ExcitationArray

DetectionArray

How to make sure the incident SPP wave is planar?

Image with Fresnel zone plate

Image without Fresnel zone plate

Diffractive SPP focusingDiffractive SPP focusing

High intensity focused SPP field is observed

SPP focusing SPP focusing after the compensation of radiation loss

x (m)

y (

m)

Focusing with Radiation Loss

-100 -50 0 50 100

-100

-80

-60

-40

-20

0

20

40

60

80

100-100 -50 0 50 100

-100

-80

-60

-40

-20

0

20

40

60

80

100Focuing without Radiation Loss

x (m)

y (

m)

x (m)

y (

m)

Focusing with Radiation Loss

-100 -50 0 50 100

-100

-80

-60

-40

-20

0

20

40

60

80

100

x (m)

y (

m)

Focusing with Radiation Loss

-100 -50 0 50 100

-100

-80

-60

-40

-20

0

20

40

60

80

100

Measured focal length: 83μm Designed focal length: 80μm

Fresnel diffraction of SPPFresnel diffraction of SPP

Fresnel diffractionFresnel diffraction

20 0 0 0

exp( )( , ) ( ) exp( ( ) )

2spp spp

spp T

ik x iku x y u y y y dy

i x x

20 0 0 0

exp( )0.3 ( )exp( ( ) )

2spp spp

spp O

ik x iku y y y dy

i x x

FEM Simulation:FEM Simulation:

Transmission through Si bumps

Power Transmission ~ 0.3

-50 -40 -30 -20 -10 0 10 20 30 40 500.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Op

tica

l Sig

na

l (a

.u.)

y (m)

-50 -40 -30 -20 -10 0 10 20 30 40 500.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Op

tica

l Sig

na

l (a

.u.)

y (m)

Calculated vs Measured Field

Diffraction theory is valid for SPP

-50 -40 -30 -20 -10 0 10 20 30 40 500.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Opt

ical

Sig

nal (

a.u.

)

y (m)

Fresnel Diffraction CalculationFresnel Diffraction Calculation MeasurementMeasurement

Field intensity distribution at the focal planeField intensity distribution at the focal plane

Time-resolved SPP focusingTime-resolved SPP focusingSnapshots of amplitude at different timeSnapshots of amplitude at different time

Education, Outreach, and Data Dissemination

• 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

L. Feng, K. Tetz, B. Slutsky, V. Lomakin, Y. Fainman, Appl. Phys. Lett. 91, 081101 (2007)

L. Feng, K. Tetz, B. Slutsky, V. Lomakin, Y. Fainman, Appl. Phys. Lett. 91, 081101 (2007)

Imaging various SPP modesa/

polarizers //to (2, 1) type modes

ASE: = 1520-1570 nm

(-X) (-X)0.90

1.03

1.41noise limited spectral measurements

2.00

Fainman Y, Tetz K, Rokitski R, Pang, Optics & Photonics News, vol.17, 24-9, 2006