Yehiam Prior Department of Chemical Physics Weizmann Institute of Science With Adi Salomon Weizmann Institute Rehovot Joseph Zyss Marcin Zielinsky ENS Cachan France Maxim Sukharev ID: 1042109
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1. Nonlinear Optical Response of Nanocavities in Thin Metal FilmsYehiam PriorDepartment of Chemical PhysicsWeizmann Institute of ScienceWith Adi Salomon - Weizmann Institute, RehovotJoseph Zyss, Marcin Zielinsky - ENS Cachan, FranceMaxim Sukharev - Arizona State University, ArizonaTamar Seideman - Northwestern University, IllinoisRobert Gordon - University of Illinois, Illinois Israel Chemical Society Annual Meeting February 2012
2. Nano ParticlesNotre Dame, ParisQuantum size effectGold nanoparticlesSemiconductor nanoparticles
3. Nano “structures”
4. Transmission with d<<λWhen arrays are used – sharp interference peaks are observedThe transmitted intensity is much larger than classical [~(d/λ)4]Explained in terms of Plasmonic excitations in the metalNano Holes
5. The periodicity determines the colorTransmission through an array of nano holespSEM
6. We understand the linear optical properties of these structures fairly well.What about their NONLINEAR optical properties?
7. OUTLINESHG from Individual cavitiesFrom isolated to coupled cavitiesPlasmon-molecule interactionsConclusions and future directions
8. OUTLINESHG from Individual cavitiesFrom isolated to coupled cavitiesPlasmon-molecule interactionsConclusions and future directions
9. Focused Ion Beam (FIB) fabricated shapes
10. What is the SHG response of a nano-hole ?Ag film ~ 200nm, evaporated on glass
11. SHG from non interacting trianglesω2ωExperimental set-up
12. 150nm SHG from Individual triangles with different side length 170nm 190nm 220nm 245nm 285nm
13. SHG from Individual triangles with different side lengthExperimental condition: 200nm Ag film evaporated on glass (n = 1.5)FW=940nm thus SHG at 470nm
14. SHG from Individual holes - size dependence
15. SHG from Individual holes – wavelength dependencea=210nm
16. An oversimplified modelFor equilateral triangular cavities: For square cavities: Fabry-Pérot “bouncing ball” :“diamond-like” :
17. An oversimplified model
18. SHG Polarization propertiesPhoto diode/xPhotoDiode/y
19. Polarization properties for an individual cavity
20. OUTLINESHG from Individual cavitiesFrom isolated to coupled cavitiesPlasmon-molecule interactionsConclusions and future directions
21. What happens when the holes are closer to each other, and are allowed to interact?We observe a gradual transition from isolated holes to coupled ones (similar to the assembly of a crystal from individual molecules)The intensity, as well as the polarization properties changeFrom individual to coupled cavities
22. Individual holeCoupled holesFrom individual to coupled cavities
23. (a) (b)(c)From individual to coupled cavities: Polarization
24. cbadFrom individual to coupled cavities: Polarization(a) (b) (d) 5000 10000 150003021060240902701203001503301800(c)
25. From individual to coupled cavities: Intensity Individual (650nm) coupled (450nm)SilverGold
26. From individual to coupled cavities: λ dependenceSmaller signal for shorter wavelengths
27. From individual to coupled cavities: observationsIndividual holes give rise to SHGTwo types of coupling:“Light only” coupling – the plasmons generated in different holes do not interact directly (i.e. the gold sample), the dependence on the number of holes is quadraticPlasmon coupling - the plasmons interact directly, the dependence on the number of holes is more than quadraticIn both cases, the coupling is characterized by different polarization propertiesFor direct plasmonic coupling, metal must support plasmonic propagation at both the fundamental and the second harmonic frequencies
28. 123123Hot Spots
29. 123123Hot Spots
30. 1Hot SpotsGiant SHG signals at the hot spots (almost 1000 times bigger)
31. OUTLINESHG from Individual cavitiesFrom isolated to coupled cavitiesPlasmon-molecule interactionsConclusions and future directions
32. Plasmon-molecule interaction – the system
33. Energy[eV]Slit array periodicity [nm]Transmission[a.u.]WaveVector[m-1]Energy [ev] Molecular state Upper polariton Lower polaritonPlasmon-molecule interaction – avoided crossing
34. WaveVector [m-1]Energy [eV](a)(b)o Collective mode Molecular state Upper polariton Lower polaritonEnergy [eV]Transmission [a.u.]Plasmon-molecule interaction – strong coupling
35. Energy [eV]Spacer thickness[nm]Plasmon-molecule interaction – strong coupling, with a spacer layer
36. OUTLINESHG from Individual cavitiesFrom isolated to coupled cavitiesPlasmon-molecule interactionsConclusions and future directions
37. Conclusions and future directionsWe observed coherent SHG from individual nanocavitiesSize and shape matter - resonances are observedTwo types of coupling: light mediated and plasmon mediated, giving rise to a gradual transition to a “crystal”Polarization properties provide excellent characterizationAdditional experiments and theory are needed to fully and quantitatively understand the resultsCalculations for strong coupling with moleculesEngineered (nonlinear) optical properties are possible Hot spots are observed, with a potential for high sensitivity spectroscopy (to the single molecule level ?)
38. Thank you
39. Hot SpotsGiant SHG signals at the hot spots (almost 1000 times bigger)
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42. 123123Hot Spots
43. 10D20D30D40D1e245e241e255e263e25Figure 3:(a) (b) Energy [eV]Energy [eV]Transmission [a.u.]Transmission [a.u.]Dipole moment [Debye]RS (meV) M density [m-3]RS (meV)