SPECTRAL AND DISTANCE CONTROL OF QUANTUM DOTS TO PLASMONIC NANOPARTICLES INTERACTIONS P. Viste, J. Plain, R. Jaffiol, A. Vial, P. M. Adam, P. Royer ICD/UTT Troyes, Laboratoire de Nanotechnologie et d’Instrumentation Optique, France

Introduction : to plasmonics !. Surface Plasmon Polaritons on nanowaveguides : excitation, propagation, control and detection main issues : lateral confinement and propagation distance. Localized Surface Plasmons on metallic nanoparticles : coupling to quantum emitters main issues : enhancement and directivity of the emission (weak coupling)

Introduction Fluorescence lifetime modification of Eu ions in front of a silver mirror Drexhage K.H. progress in Optics (Wolf (E.) Near field versus far field coupling. Lifetime reduction is accompanied by photoluminescence quenching !

Introduction Fluorescence enhancement at the single molecule level Enhancement of 1000 A. Kinkhabwala et al, Nature Phot. 3, 654 (2009)

Introduction P. Pompa et al, Nature Nanotechnology 1, 128 (2006) J. H. Song et al, Nano Lett. 5 (8), 1557 (2005) Quantum Dots luminescence enhancement vs. quenching on metal nanostructures A systematic and parametric study is needed

S / S 0 = (η/η 0 ) (|p. E loc | 2 / |p· E 0 | 2 ) Introduction S 0 : fluorescence signal without the metallic nanoparticles S : fluorescence signal with the metallic nanoparticles E loc : local electric field can be enhanced through :. Localized Surface Plasmon (LSP) Resonance. lightning rod effect at sharp edges. nanogaps

Quantum yield η 0 =  r0 /(  nr0 +  r0 ) η=  r /(  nr0 +  r +  nr ) Introduction  r : radiative relaxation rate of the system metallic nanoparticle / molecule  nr : nonradiative relaxation rate of the molecule in the metallic nanoparticle Increase or decrease of luminescence depends on interplay between E loc,  r,  nr and thus on the Nanoparticle geometry and LSP resonance!

Experiments : QDs on Plasmonic NanoParticles (PNP)

Plasmonic NanoParticles fabrication e-e- e-beam lithographynanolithographied maskmetal evaporation lift off

The plasmon resonance is controlled over a wide spectral range (depends on the height to diameter ratio): below and above the QD emission peak Gold nanocylinders

Absorption and emission spectra of CdTe/CdS/TOPO Quantum Dots Absorption of the QD Emission of the QD : 665 nm peak TOPO organic ligands CdS shell CdTe core Wavelength (nm) No LSP resonance at the excitation wavelength (405 nm) !

Measured QD photoluminescence on different PNP patterns 140nm 130nm Bare QD 80nm Quantum dots in PMMA Collection area =1μ 2 Excitation wavelength : 405 nm

PL modification factor F as a function of the PNP diameter for gold and silver Enhancement of the PL by a factor 2.6 Photoluminescence enhancement and quenching PNP diameter (nm)

Modification factor of QD luminescence for gold nanocylinders Enhancement when the emission of the QD (665 nm) is close to the LSP resonance Wavelength (nm) Luminescence in absence of the nanocylinders F

Discussion Resonant behaviour of the QD photoluminescence when coupled to gold nanocylinders : increase of η Enhancement occurs when the emission is blue shifted (40 nm) with respect to the LSP resonance LSP resonance is obtained through plane wave excitation PNP is excited by the near-field of the emission dipole - Colas des Francs, G, et al. Optics Express, 16, 22, (2008) - Bharadwaj, P., Novotny, Optics Express, 15, 21, (2007 ).

Interdistance QD-PNP influence

PL modification as a function of the interdistance R PNP EnhancementPNP Quenching R decreasing

PL modification factor F as a function of the MNP - QD interdistance for gold PNP of 80nn, 100nm, 120nm, 130nm, 140nm and 160nm. PL modification as a function of the interdistance

QD - MNP coupling efficiency as a function of the interdistance R. E(R) shows a R -6 dependency

Quenching : non radiative energy transfer from the QD to the PNP : - if R > > PNP diameter : dipole - dipole coupling : 1/r 6 law - if R < < PNP diameter : plane - dipole coupling : 1/r 3 law QD Emitter couples to a protrusion on the PNP ! Discussion M. Thomas, J.-J. Greffet, R. Carminati, J. R. Arias-Gonzalez Appl. Phys. Lett. 85, 3863 (2004)

Enhancement : two types - Coherent interference of radiations of the emission dipole and the induced dipole in the PNP : 1/r 3 law - Energy transfer from the emission dipole to the PNP followed by radiation of the PNP : 1/r 6 law Discussion M. Thomas, J.-J. Greffet, R. Carminati, J. R. Arias-Gonzalez Appl. Phys. Lett. 85, 3863 (2004)

Conclusions Control of enhancement or quenching of the PL through the plasmonic nanoparticle size and resonance Near field coupling of the QD to the PNP accompanied by non radiative energy transfer P. Viste et al. ACS Nano. 4, 759 (2010)

Outlooks PNP induced modification and control of the luminescence radiation pattern : nanoantenna concept Huge enhancements of luminescence with plasmonic nanocavities Single QD intensity and lifetime measurements Complete model of the emitter/PNP system