Electrically-Driven Optical Antennas V · - Connected nanoantenna + functionalized particle - Light...

Electrically-DrivenOptical Antennas

René Kullock, Johannes Kern, Jord Prangsma and Bert Hecht

V+

hν

J.C. Prangsma et al., Electrically connected resonant optical antennas, Nano Lett. (2012)

50 nm

Motivation

2

On-chip data communication

Ultra-high density displays

Spectroscopic applicationsV+

hν

50 nm

How to Generate Light?

3

Processes:

- thermal

- electronic transitions

How to Generate Light?

4

Processes:

- thermal

- electronic transitions

- Inelastic electron tunneling

-> “Just” a tunnel gap is needed

Fabrication of the Tunnel Gap

5

cu

rren

t (a

.u.)

0

1

distance (nm)

0 2 4 6 8 10

Requirements:

- 1-3 nm gap width

- Atomic-scale stability

Fabrication of the Tunnel Gap

66

Requirements:

- 1-3 nm gap width

- Atomic-scale stability

Ga-Ion Focused Ion Beam Milling:

- Single-crystalline gold flakes

- Resolution limit around 15 nm

- Leakage currents

Solution:

- Stable 1-nm gaps for CTAB decorated nanoparticles

Fabrication of the Tunnel Gap

7J. Huang et al., Atomically flat single-crystalline gold nanostruct. for plasmonic nanocircuitry, Nature Com. (2010)

J.C. Prangsma et al., Electrically connected resonant optical antennas, Nano Lett. (2012) 7

Requirements:

- 1-3 nm gap width

- Atomic-scale stability

Ga-Ion Focused Ion Beam Milling:

- Single-crystalline gold flakes

- Resolution limit around 15 nm

- Leakage currents

Solution:

- Stable 1-nm gaps for CTAB decorated nanoparticles 1 nm20 nm

a b

J. Kern et al., Atomic-scale confinement of resonant optical field, Nano Lett. (2012)

Fabrication of the Tunnel Gap

8

New Approach:

- Pushing CTAB decorated nanoparticle into the antenna gap

CTABCetrimonium bromide

Results

9

- Nanometer-scale gap formed

- Tunneling characteristics

- Particle positioned asymmetrically

-> only one significant contact

linear tunneling regime

field emission regime

VT

~1 GV/m

~100 Ω

500 nm

- Light detected: 500…1000 nm

- Typical spot sizes: 300…400 nm

-> Electrically-driven point source!

Electroluminescence (EL)

10

350 nm

1000

500

0

-500

-1000

Influence of the Antenna

- EL is shaped by the antenna resonance

WL scattering

Exp Model

0

2

4

6

8

0

5

10

15

20

Wavelength (nm)

500 600 700 800 900 1000

Energy (eV)2.4 2.2 2 1.8 1.6 1.4

EL in

ten

sity

(10

3P

ho

ton

/s)

Scat

teri

ng

amp

litu

de

(%

)

1.7V1.8V1.9V2.0V

Influence of the Antenna

- EL is shaped by the antenna resonance

- QE up to 100x enhanced

- Polarized emission

- Dipolar emission pattern

12

Modelling?

- How to understand the light-emission process?

- And the spectral shift?

Modelling: Quantum shot noise

electrons in

electrons in

electrons reflected

electrons trans

+ -

electrons in

electrons reflected

electrons trans

+-

Modelling: Quantum shot noise

electrons in

electrons in

electrons reflected

electrons trans

Hone, Muhlschlegel, and Scalapino, Appl. Phys. Lett. 33, 203 (1978).P. Johansson, Physical Review B 58, 10823 (1998).Schneider, Schull, and Berndt, Phys. Rev. Lett. 105, 026601 (2010).

current power spectrum:

𝐼 𝜔 = 𝐴 𝜔 𝐶(𝜔)

Modelling: Quantum shot noise

current power spectrum:

Wavelength (nm)

1000

3.0V

2.0V1.9V

1.8V

1.7V

Cu

rre

nt

Po

we

rx

Lore

ntz

ian

(a.u

. )

0

1

2

3

4

5

No

rma

lize

dsc

a tte

rin

ga

mp

litu

de

0

1

Wavelength (nm)

500 600 700 800 900 1000

Energy (eV)

2.4 2.2 2 1.8 1.6 1.4

WL spectrumLorentzian fit

2.0V

1.9V

1.8V

1.7V

3.0 V

x 0.39

Cu

rre

nt

Po

we

rS

pe

c tru

m

0

0.2

0.4

0.6

0.8

1

500 600 700 800 900

Energy (eV)2.4 2.2 2 1.8 1.6 1.4

Hone, Muhlschlegel, and Scalapino, Appl. Phys. Lett. 33, 203 (1978).P. Johansson, Physical Review B 58, 10823 (1998).Schneider, Schull, and Berndt, Phys. Rev. Lett. 105, 026601 (2010).

𝐼 𝜔 = 𝐴 𝜔 𝐶(𝜔)

Modelling: Quantum shot noise

current power spectrum:

Wavelength (nm)

1000

3.0V

2.0V1.9V

1.8V

1.7V

Cu

rre

nt

Po

we

rx

Lore

ntz

ian

(a.u

. )

0

1

2

3

4

5

No

rma

lize

dsc

a tte

rin

ga

mp

litu

de

0

1

Wavelength (nm)

500 600 700 800 900 1000

Energy (eV)

2.4 2.2 2 1.8 1.6 1.4

WL spectrumLorentzian fit

2.0V

1.9V

1.8V

1.7V

3.0 V

x 0.39

Cu

rre

nt

Po

we

rS

pe

c tru

m

0

0.2

0.4

0.6

0.8

1

500 600 700 800 900

Energy (eV)2.4 2.2 2 1.8 1.6 1.4

Hone, Muhlschlegel, and Scalapino, Appl. Phys. Lett. 33, 203 (1978).P. Johansson, Physical Review B 58, 10823 (1998).Schneider, Schull, and Berndt, Phys. Rev. Lett. 105, 026601 (2010).

Conclusion- Built an electrically-driven subwavelength light source

- Connected nanoantenna + functionalized particle

- Light emission governed by the antenna

- QE enhanced by up to 100x

- Quantum shot noise

Outlook- Directed emission via Yagi-Uda antennas

- Improve stability, QE, …

- Launch propagating plasmons

- Usable for field-induced non-linearity

100 nm

Ack

no

wle

dge

me

nts Electrode Structures Monika Emmerling

Flake Transfer Heiko Groß

Flake Growth Xiaofei Wu

Enno Krauss

FIB Provider Martin Kamp

Connected Antennas Jord Prangsma

Pushing Johannes Kern

Optics Swen Großmann

Bert Hecht

Johannes Kern

Jord Prangsma

kullock@physik.uni-wuerzburg.de

1 µm

10 µm

100 µm

1 mm

10 nm1 nm

http://arxiv.org/abs/1502.04935