BRIGHT NEW WORLD

NORBERT KROO

HUNGARIAN ACADEMY OF SCIENCES

DUBNA, 25.09.2008

TheThe Lycurgus Lycurgus CupCup ( (glassglass; British ; British Museum; 4Museum; 4thth CenturyCentury A. D.) A. D.)

When illuminated from outside, it appears green. However, whenilluminated from within the cup, it glows red. Red color is due to very small amounts of gold powder (about 40 parts per million)

Surface plasmon oscillationsMesoscopic:~1011 electrons

SURFACE PLASMON POLARITONS are a

„NEW TYPE OF LIGHT”, they are

1.BOUND TO THE (METAL) SURFACE,

2.HAVE SPECIFIC DISPERSION PROPERTIES,

3.THE DIFFRACTION LIMIT DOES NOT APPLY,

4. MAY BE GUIDED,

5.REPRESENT VERY HIGH ELECTRIC FIELDS,

6.MAY BE LOCALIZED (e.g. to nanospheres or nanoshells)

7.MAY HAVE A BANDGAP,

8.MAY BE THE SUBJECT OF NONLINEAR PROCESSES

9. SHOW NON-CLASSICAL PROPERTIES

A POTENTIAL BASIS OF FUTURE NANOOPTICS

ELECTRIC FIELD OF SURFACE PLASMONS

From Maxwell’s equations

1

2

Excitation of SPO-s !!!?

TYPICAL RESPONSE SIGNALS AND THEIR PART

USED FOR IMAGING

↓

thermal

SPO

LASER PULSE EXCITED

SURFACE PLASMON NEAR FIELD STM

3

23870

Ag SURFACE, W tip

200x200nm

Topographic, SPO and thermal images

SURFACE PLASMON LIGHT GUIDE

38590+92

4000x4000nm

Gold images

Cut from

5000x5000nm images

4

5GIANT ELECTRIC FIELDS!

34300+02 Au

Cut from 200x200nm

images

100x100nm

Gold

Topography and

SPO near field

STM images

6

WHAT IS THE ORIGIN OF THE COLORWHAT IS THE ORIGIN OF THE COLOR OF THE OF THE

LYCURGUS CUPLYCURGUS CUP? ANSWER: ``SURFAC? ANSWER: ``SURFACE E PLASMONS’’PLASMONS’’ An SPAn SPOO is a natural oscillation of the electron gas inside a is a natural oscillation of the electron gas inside a goldgold

nanospherenanosphere.. SPSPOO frequency depends on the frequency depends on the dielectricdielectric functionfunction of the gold, and the of the gold, and the

shapeshape of the nanoparticle. of the nanoparticle. For a For a spheresphere the plasma frequency is about the plasma frequency is about 0.580.58 times the bulk times the bulk

plasma frequency (being in the UV; the SPO frequency is in the plasma frequency (being in the UV; the SPO frequency is in the visible)visible) (~520nm) (~520nm)

electron sphere

Ionic background

Electron cloud oscillates with frequency of the SPO-s; ions provide restoring force.

(not to scale)

SURFACE PLASMON ENERGY, OR MOMENTUM „GAPS”

Donor (chromophore), Acceptor (fluorophore)

7

B:Similar arrangement, but simpler electronics for angular and spectral property studies of pulsed (790nm, 120fs) laser excited SPO emitted light

1.ARRANGEMENT FOR ANGULAR, LASER POWER AND TIME DEPENDENCE

MEASUREMENTS (A)

808nm SEMICONDUCTOR LASER

8

23870

Ag SURFACE, W tip

200x200nm

9

23950ss

FFT OF THE TOPOGRAPHIC

SURFACE PLASMON AND THERMAL

IMAGES

SQUEEZING IN THE SPO IMAGE

w = 4%

APPLICATIONS OF LOCALIZED PLASMONS

THANK YOU FOR YOUR ATTENTION