Surface plasmon nanophotonics: optics below the diffraction limit

Surface plasmon nanophotonics:

optics below the diffraction limit

Albert Polman

Center for nanophotonics

FOM-Institute AMOLF, Amsterdam

Jeroen Kalkman Hans Mertens Joan Penninkhof Rene de Waele Teun van Dillen

Jen Dionne

Luke Sweatlock Harry Atwater

Arjen Vredenberg Christina Graf

Alfons van Blaaderen

Photonic integrated circuits on silicon

1 mm

SiO₂/Al₂O₃/SiO₂/Si

The world’s smallest erbium-doped optical amplifier

1.53 µm signal, 1.48 µm pump, 10 mW, gain: 2.3 dB Waveguide spiral size: 1 mm2

minimum bending radius > 50 µm

From a FOM/PPM prototype to a 40 M$ company …

Symmorphix Sunnyvale CA, USA

The first Er laser on Si fully made with CMOS technology 1500 1550 1600 -60 -50 -40 -30 -20 S ign al ( d B m ) Wavelength (nm) Single-mode lasing

with K. Vahala group, CALTECH Appl. Phys. Lett. 84, 1037 (2004) Phys. Rev. A 70, 033803 (2004)

Nanophot

onic materials gr

ou

Surface plasmon: EM wave at metal-dielectric interface z x (k x k z t) i _{x z}

e

E

t

z

x

E

r

(

,

,

)

=

r

"

'

_⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

+

=

+

=

c

ik

k

k

ε

ε

ε

ε

ω

Dielectric constants for silver: ε = ε’ _{+ iε’’} 200 400 600 800 1000 1200 1400 1600 1800 -150 -100 -50 0 50 Measured data: ε' ε" Drude model: ε' ε"

Modified Drude model:

ε' ε" ε Wavelength (nm) ε' bound SP mode: ε_m’< -ε_d -ε_d

ω

Surface plasmons dispersion:

large k small wavelength Ar laser: λ_vac = 488 nm λ_diel = 387 nm λ_SP = 100 nm Ag/SiO₂ X-ray wavelengths at optical frequencies 2 / 1 ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + = d m d m x c k ε ε ε ε ω 3.4 eV (360 nm)

SPs can have very long propagation distance 100 µm High loss in region of small λ_SP Tune SP dispersion with index dielectric

Photonic integrated circuits on silicon

1 mm

SiO₂/Al₂O₃/SiO₂/Si

Plasmonic

Al

Opto-electronic integration, (e.g. interconnects) Plamonic nanolithography

Surface plasmons can improve solid state lighting interaction between plasmon and radiating dipole

1450 1500 1550 1600 1650 0.0 0.2 0.4 0.6 0.8 1.0 0 5 10 15 20 25 e-3 e-2 e-1 e0 Energy (eV) N or m alized PL int en si ty Wavelength (nm) 0.84 0.82 0.8 0.78 0.76 4_I 15/2 4_I 13/2 Silver Air φ= 1.0 Er/cm2 Normalized intensit y Time (ms) 500 keV Er silver glass glass

far-field emission

metal

W_rad

W_SP

Coupling to surface plasmons

10-1 100 101 102 103 104 105 106 1E-3 0.01 0.1 1 10 10-1 100 101 102 103 104 105 0 250 500 750 1000 1250 1500 0.0 0.5 1.0 1.5 W_nr W_SP W_rad W_total Er distribution G lass S ilv e r G lass Ai r Distance (nm)

Normalized decay rate

0.6 0.8 1.0 W_rad Power k (k_glass)

Decay rate as a function of distance to metal

λ=1535 nm 0.0 10.0 20.0 30.0 0.13534 0.36788 1 2.71828 Air τ=9.3 ms Ag τ=5.8 ms ln(norm a lize d int ensity) time (ms) Decay near Ag is faster than in air

Si quantum dots at different depths: theory & experiment 0 200 400 600 1xe-4 1xe-3 1xe-2 1xe-1 1xe0 Ag Air PL intens ity Time (µs) λ=750 nm, d=40 nm 0 100 200 300 400 500 600 700 0.0 1.0 2.0 3.0 4.0 Exc ess Si (10 21 Si/cm 3 ) Depth (nm) 0.8 1.0 1.2 1.4 1.6 λ_em=750 nm silver-glass interface air-glass interface No rmalized de ca y rate 0 100 200 300 400 0 1 2 3 Depth (nm) λ_em=750 nm Air Ag Decay rate (10 4 s -1 ) Coupling to SPs

far-field emission metal recycling of a non-radiative decay path! W_rad W_SP W_rad+W_SP QE ∼1

Turning a slow emitter into a fast emitter

Applications:

Fast modulation of Er LEDs, Si quantum dot LEDS Increased quantum efficiency of solid state emitters

Ag

• Erbium ions implanted in silica glass substrate • Grating etched in silica

• Ag film deposited

SiO₂

Herasil glass - 250 µm thick

350 keV keV Er, 1.2×1015_cm-2 , _{77 K}

Thermal anneal 800 °C, 1 hr e-beam lithography, dry etching grating: p=1070±1 nm, d=230 nm Ag sputter evaporation (t=300 nm)

λ_pump=488 nm

θ

PL intensity as a function of angle (λ=1534 nm) 0 20 40 60 80 Angle θ (o) 's' 's' Angle θ (o) 0 20 40 60 80 0 2 4 6 'p' 'p' PL Intensity

Dispersion of thin-film surface plasmons

Two surface plasmon modes

L -L_-(symm) Thinner film: Shorter SP wavelength Example: λ_HeNe = 633 nm λ_SP = 60 nm L₊(asymm)

Thin-film surface plasmons: propagation length

More loss for thinner films

Less loss for thinner films

L_-(symm)

L₊(asymm)

Dispersion-controlled plasmonic devices 0 200 4 00 600 80 0 1000 -1. 0 -0. 5 0. 0 0. 5 1. 0 Y Ax is T it le Distance (nm) Plasmonic concentrator Si Ag NC Small λ_SP Large field enhancement v_group=0 Electrically pumped single-mode SP source Plasmonic lens

thin section _{Surface plasmon laser}

Si Ag

ε_m = 2.2

Low frequency

Er

On resonance

Er

The ultimate confinement of light:

surface plasmons in metal nanoparticles

Electromagnetic energy

transfer well below diffraction

limit → high integration density: true nanophotonics

Surface-enhanced Raman scattering Surface-enhanced fluorescence

single molecule detection

(S. A. Maier et al.) Metal nanoparticles

Molecules SiO₂

Tuning the plasmon resonance by shape: core-shell colloids 30 MeV Cu 3×1014 _cm-2 Adv. Mater. 16, 235 (2004) Au/SiO₂ 500 nm 400 600 800 1000 1200 1400 1600 0.6 0.7 0.8 0.9 1.0 extinction [a. u .] λ [nm] SiO₂/Ag nm

10 nm 30 MeV Si

9x1014_/cm2

s-pol

p-pol Modeling plasmon resonances in particle arrays

Phys. Rev. B., in press (2005)

5000-fold enhancement

field concentration: r=3 nm (3 dB)

Nanophot

onic materials gr

ou

p

Final goal: surface plasmon nanophotonic waveguides

500 nm

Plasmonics: energy transfer and confinement of light below the diffraction limit

500 nm

Group leaders • A. Polman • K. Kuipers • A. Lagendijk • W.L. Vos • J. Verhoeven • A. Tip • NN (Philips) Total staff 45 fte

Center for Nanophotonics

Fundamental Reseach & Innovation

Center for Nanophotonics – FOM-Institute AMOLF

Nanophotonics is a unique field of research because it combines a wealth of scientific challenges

with a large variety of near-term applications. Fundamental concept Prototype component Materials development Transfer to industry

www.erbium.nl Conclusions µm km mm photonics plasmonics