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 PPM conference, Utrecht, 10-2-2005
Optical fiber: long distance communication
Photonic integrated circuits on silicon SiO 2 /Al 2 O 3 /SiO 2 /Si 1 mm with C. van Dam, M.K. Smit, TUD
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 mm 2 minimum bending radius > 50 µm Appl. Phys. Lett. 68, 1886 (1996)
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 Single-mode lasing -20 Nanophotonic materials group Signal (dbm) -30-40 -50-60 1500 1550 1600 Wavelength (nm) with K. Vahala group, CALTECH Appl. Phys. Lett. 84, 1037 (2004) Phys. Rev. A 70, 033803 (2004)
Surface plasmon: EM wave at metal-dielectric interface z x ( ) t z k x k i z x e E t z x E ω = 0 ),, ( r r 2 1/ " ' + = + = d m d m x x x c ik k k ε ε ε ε ω = ε ω c k
Dielectric constants for silver: ε = ε + iε 50 0 ε" -ε d ε -50-100 -150 Measured data: ε' ε" Drude model: ε' ε" bound SP mode: ε m < -ε d Modified Drude model: ε' 200 400 600 800 1000 1200 1400 1600 1800 Wavelength (nm) ε'
Surface plasmons dispersion: ω ck x ε d k x = ω ε mε d c ε m + ε d 1/ 2 large k small wavelength 3.4 ev (360 nm) Ag/SiO 2 Ar laser: λ vac = 488 nm λ diel = 387 nm λ SP = 100 nm X-ray wavelengths at optical frequencies Re k x
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 Plasmonic SiO 2 /Al 2 O 3 /SiO 2 /Si Al Opto-electronic integration, (e.g. interconnects) Plamonic nanolithography 1 mm 10 µm
Surface plasmons can improve solid state lighting interaction between plasmon and radiating dipole 500 kev Er e 0 φ= 1.0 Er/cm 2 glass glass silver Normalized intensity e -1 e -2 e -3 Normalized PL intensity 1.0 0.8 0.6 0.4 0.2 Energy (ev) 0.84 0.82 0.8 0.78 0.76 0.0 1450 1500 1550 1600 1650 Wavelength (nm) 4 I 13/2 4 I 15/2 Silver Air 0 5 10 15 20 25 Time (ms)
Coupling to surface plasmons W rad far-field emission W tot = W rad + W SP W SP metal
Decay rate as a function of distance to metal 1.0 Air Glass 10 6 10 5 W rad 10 4 Normalized decay rate 0.8 0.6 1.5 1.0 0.5 0.0 Silver Glass Er distribution W total W rad W SP W nr 0 250 500 750 1000 1250 1500 Distance (nm) λ=1535 nm Power 10 3 10 2 10 1 10 0 10-1 10 5 10 4 10 3 10 2 10 1 10 0 10-1 1E-3 0.01 0.1 1 10 k (k glass ) ln(normalized intensity) 2.71828 1 0.36788 0.13534 Ag τ=5.8 ms Air τ=9.3 ms 0.0 10.0 20.0 30.0 time (ms) Decay near Ag is faster than in air Appl. Phys. Lett. in press (2005)
Si quantum dots at different depths: theory & experiment Normalized decay rate 1.6 1.4 1.2 1.0 0.8 silver-glass interface air-glass interface λ em =750 nm PL intensity 1xe 0 1xe -1 1xe -2 1xe -3 Ag λ=750 nm, d=40 nm Air Excess Si (10 21 Si/cm 3 ) 4.0 3.0 2.0 1.0 0.0 0 100 200 300 400 500 600 700 Depth (nm) Coupling to SPs 1xe -4 Decay rate (10 4 s -1 ) 3 2 1 0 200 400 600 Air Ag Time (µs) λ em =750 nm 0 0 100 200 300 400 Depth (nm)
Turning a slow emitter into a fast emitter W rad W rad +W SP far-field emission W SP recycling of a non-radiative decay path! QE 1 metal Applications: Fast modulation of Er LEDs, Si quantum dot LEDS Increased quantum efficiency of solid state emitters
Erbium ions implanted in silica glass substrate Grating etched in silica Ag film deposited λ pump =488 nm Herasil glass - 250 µm thick 350 kev kev Er, 1.2 10 15 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) θ SiO 2 Er Ag
PL intensity as a function of angle (λ=1534 nm) 6 PL Intensity 4 2 's' 'p' 'p' 's' 0 0 20 40 60 80 Angle θ ( o ) 0 20 40 60 80 Angle θ ( o ) Appl. Phys. Lett. 83, 4137 (2003)
Dispersion of thin-film surface plasmons Two surface plasmon modes Thinner film: Shorter SP wavelength Example: λ HeNe = 633 nm λ SP = 60 nm L - L - (symm) L + (asymm)
Thin-film surface plasmons: propagation length L - (symm) L + (asymm) More loss for thinner films Less loss for thinner films Challenge: fabricate smooth thin metal films
Dispersion-controlled plasmonic devices Electrically pumped single-mode SP source Ag NC Si Plasmonic concentrator Y Axis Title 1. 0 0. 5 0. 0-0. 5-1. 0 Small λ SP Large field enhancement v group =0 Plasmonic lens 0 200 4 00 600 80 0 1000 Distance (nm) thin section Surface plasmon laser Ag NC Si
The ultimate confinement of light: surface plasmons in metal nanoparticles Low frequency On resonance ε m = 2.2 E r E r SiO 2 Molecules Metal nanoparticles Surface-enhanced Raman scattering Surface-enhanced fluorescence single molecule detection (S. A. Maier et al.) Electromagnetic energy transfer well below diffraction limit high integration density: true nanophotonics
Tuning the plasmon resonance by shape: core-shell colloids nm Au/SiO 2 SiO 2 /Ag 1.0 500 nm extinction [a.u.] 0.9 0.8 0.7 0.6 30 MeV Cu 3 10 14 cm -2 400 600 800 1000 1200 1400 1600 λ [nm] Adv. Mater. 16, 235 (2004) Adv. Mater. In press (2005)
Modeling plasmon resonances in particle arrays 10 nm 30 MeV Si 9x10 14 /cm 2 s-pol p-pol 5000-fold enhancement field concentration: r=3 nm (3 db) Phys. Rev. B., in press (2005) Appl. Phys. Lett. 83, 4137 (2003)
Final goal: surface plasmon nanophotonic waveguides nm 500 nm 500 nm Nanophotonic materials group Plasmonics: energy transfer and confinement of light below the diffraction limit
Fundamental Reseach & Innovation Center for Nanophotonics FOM-Institute AMOLF Center for Nanophotonics Group leaders A. Polman K. Kuipers A. Lagendijk W.L. Vos J. Verhoeven A. Tip NN (Philips) Total staff 45 fte Fundamental concept Materials development Nanophotonics is a unique field of research because it combines a wealth of scientific challenges with a large variety of near-term applications. Prototype component Transfer to industry
km Conclusions mm www.erbium.nl µm photonics plasmonics