Optics, Plasmonics and Excitonics: Connecting Fundamental Theory to Experiments and Applications

Transcription

1 Emerging Topics in Optics University of Minnesota April 24, 2017 Optics, Plasmonics and Excitonics: Connecting Fundamental Theory to Experiments and Applications George C. Schatz Northwestern University

2 Metal nanoparticle optical property research Electrodynamics: Shengli Zou (Central Florida) Marty Blaber (Seagate) Montacer Dridi (France) Kevin Kohlsted Daniel Park, Mike Ross, Marc Bourgeois Danqing Wang, Weijia Wang Wendu Ding, Liang-Yan Hsu Teri Odom, Rick Van Duyne, Chad Mirkin, Emily Weiss, M. Ratner, Stephen Gray (Argonne)

3 Outline 1. Optical properties of isolated particles 2. Plasmon resonances for 1D and 2D nanoparticle arrays; lattice-plasmons and plasmon lasers 3. Plasmon resonances for 3D superlattice crystals: plasmon-photonic interactions and metamaterials properties. 4. Plasmon-mediated exciton transport

4 Colloidal Gold Michael Faraday, 1856 Spectra of dispersed colloidal gold for selected diameters (data from Turkevich (1954), Doremus (1964)) Extinction (Optical Density) nm 20 nm 5.2 nm 3.5 nm 100 nm 160 nm nm Wavelength (nm) Extinction = absorption + scattering (color of solution=color of light not absorbed or scattered)

5 Extinction Efficiency Mie Extinction for 13 nm Au spheres wavelength(nm) Plasmon excitation: collective excitation of the conduction electrons Nuclear framework of particle E-field Metal sphere Charge cloud of conduction electrons e - cloud Langmuir plasma frequency (1929): Plasmon (Bohm, Pines, 1952): ω = shape / surroundings λ sp = = 2πc chemical properties p 4πne m 1+ χε 4πne m n=electron density e χ = shape factor (2 for sphere, >2 for spheroid) ε o = dielectric constant of surroundings e 2 o 2

6 Spectrum of Colloidal Silver

7 The Plasmonic Periodic Table Blaber, et al. J. Phys: Condens. Matter, ,

8 Real or Imaginary part of dielectric constant Dielectric constants of Au 5.0 imaginary 0.0 real wavelength (nm) Extinction Efficiency Mie Extinction for 13 nm Au spheres wavelength(nm) Mie Theory (1908) (Lorenz-Mie-Debye) Theory G. Mie, Annalen der Physik, 26, , 1908 Extinction Cross Section = (long wavelength limit) 2 3 8π ( radius ) 3ε λ ( ε ) ε Gustav Mie ε = dielectric function of metal = ε 1 + iε 2 Extinction for 20 nm spheres 20 nm ε 2 ε 1

9 Size-Tunable Surface Plasmon Resonances Normalized Extinction width height shape l max Ag/mica Wavelength (nm)

10 Computational Electrodynamics Methods for Nanoparticles t 1 E = H J ε 1 H = E t µ d J t J t E t p p p p 0 dt 2 ( ) + γ ( ) = ωε ( ) Grid or Finite element methods: Discrete Dipole Approximation Finite Difference Time Domain Method Whitney-form Finite Element Method Beyond Conventional Maxwell: Nonlocal dielectric functions Coupled QM + EM

11 Discrete Dipole Approximation P=α Ee A P ik r i i 0 ij j i j Solve using iteration with complex conjugate gradient and FFT A P k r (r P ) 1 ikr r P 3r r P ikr e ij 2 ij 2 ij j = 3 ij ij j + 2 ij j ij ij j rij r ij ( ) k=ω/c, r ij = r i -r j, and r ij = (r i -r j )/r ij

12 Finite-difference Time-Domain Method ε E = H J t µ H = E t ε i+ 1/2, jk, E E n+ 1/2 n 1/2 x i+ 1/2, jk, x i+ 1/2, jk, t = H H H H y z n n n n z i+ 1/2, j+ 1/2, k z i 1/2, j+ 1/2, k y i+ 1/2, j, k+ 1/2 y i+ 1/2, j, k 1/2 µ i, j+ 1/2, k+ 1/2 H H n+ 1 n x i, j+ 1/2, k+ 1/2 x i, j+ 1/2, k+ 1/2 t E E E E = z y n+ 1/2 n+ 1/2 n+ 1/2 n+ 1/2 y i, j+ 1/2, k+ 1 y i, j+ 1/2, k z i, j+ 1, k+ 1/2 z i, j, k+ 1/2

13 Extinction E ficiency nm 15 a 16 nm nm 12 nm 15 b 16 nm Wavelength, nm Mirkin, et al, Figure 5 Silver prisms (15x75 nm) R. Jin, Y. Cao, C. A. Mirkin, K. L. Kelly, G. C. Schatz, J. -G. Zheng, Science, 294, (2001) Measured spectrum ~670 nm Extinction (a.u.) 0.05 ~480 nm 335 nm Wavelength, nm Z axis 20 Induced polarization at 670 nm y Y axis nm Calculated Spectrum 76 nm 12 nm Wavelength, nm b

14 Modeling the Spectra of Silver Bipyramids using EM Ag right bipyramid Experiments Simulations b a = 106, 131, 165, 191 nm a a = 2b Extinction Extinction Wavelength (nm) Wavelength (nm) Au rod-sheath Experiments and simulations are in good agreement with each other. Zhang, Li, Wu, Schatz, and Mirkin Angew. Chem. Int. Ed., 48, 7787, (2009)

15 Precision test of electrodynamics for silver cubes 90 nm Ag cube on glass: Plasmon is split into a blue component on the top and a red component on the bottom ~ 1 nm precision required for theory-experiment match!! McMahon, Wang, Sherry, Van Duyne, Marks, Gray, and Schatz, JPCC, 113, (2009)

16 5000 nm LSPR Control by Molecular Adsorbates: Alkanethiols Ag Extinction 0.16 CH (CH ) SH CH 3 CH 3 CH 3 Ag 0.08 Dl Δλ max = +40 nm Wavelength (nm) Van Duyne et al., J. Am. Chem. Soc., 123, (2001).

17 Surface Enhanced Raman Spectroscopy (SERS) Normal Raman Spectrum (NRS) 2.5 M Pyridine Surface - Enhanced Raman Spectrum (SERS): enhancement factor = 10 6 Surface Pyridine ω ex ω ex - ω vib Nanoparticles Nanoparticles D. L. Jeanmaire and R. P. Van Duyne, J. Electroanal. Chem. 84, 1-20 (1977)

18 Plasmon enhancement factors (electromagnetic mechanism): Absorption =~ E(ω) 2 SERS enhancement =~ E(ω) 2 E(ω ) 2 ~ ( E 4 ) ave ~ When molecule is in direct contact with surface there are also chemical enhancements in SERS

19 Arrays of Au, Ag Nanoparticles: Optical properties strongly determined by structure

20 Extinction Spectra of Nanoparticle Chains 9 Parallel polarization leads to red shifts a Extinction Efficiency 6 3 D/2r= single Coupled multipole results for nm spheres, parallel parallel polarization Wavelength (nm) E 0

21 Perpendicular polarization leads to blue shifts single c perpendicular E 0

22 Narrow lineshapes for one-dimensional arrays of silver particles spaced by the wavelength nm particles Infinite array of 50 nm particles Width=4 mev E 0 Width=0.001meV Shengli Zou, Nicolas Janel, and George C. Schatz, J. Chem. Phys. 120, (2004).

23 Particle arrays made using optical lithography show sharp lattice plasmon resonances W. Zhou and T. Odom, Nature Nano, 6, 423 (2011), A. Yang, T. B. Hoang, M. Dridi, C. Deeb, M. H. Mikkelsen, G. C. Schatz, T. W. Odom, Nature Comm 6, 6939 (2015)

24 Particle arrays made using lithography show interaction of lattice mode with a gap plasmon Experiment Theory Q-Y Lin et al (M. Ross, GCS, C. A. Mirkin) Nano Lett, 15, 4699 (2015)

25 Al nanoparticle arrays show both dipole and quadrupole lattice plasmons A. Yang, A. J. Hryn, M. R. Bourgeois, W-K Lee, J. Hu, G. C. Schatz, T. W. Odom, PNAS 113, (2016)

26 Plasmonic Lasers Gain medium near plasmonic structure results in enhanced stimulated emission CdSe nanowire near flat silver surface Oulton,R. F. et al. (X Zhang), Nature, 461, (2009) Laser dye around spherical gold particle Noginov, M. A. et al.(shalaev, Stockman), Nature, 460, (2009) Background and Motivations 26

27 Nature Nano 8, (2013)

28 Coupling QM to EM at the rate constant level 1)Quantum treatment of dye molecules 2)Classical electrodynamics for nanoparticle array Nature Nano 8, (2013) Model components: Measured and calculated extinction Measured and calculated dispersion behavior

29 Coupling QM to EM at the rate constant level Nature Nano 8, (2013) 1) Maxwell s equations determine fields (S5) 2)Rate equations (derivable from Bloch equations) determine state populations, including amplified spontaneous and stimulated emission dn3 N3 N3 1 dpa = + E dt τ τ ω dt dn dt N N 1 dpe = + E τ τ ω dt dn1 N2 N1 1 dpe = E dt τ τ ω dt e e a dn0 N1 N3 1 dpa = + E dt τ τ ω dt a 3) Coupling of molecular polarization to field () dpa() t 2 + ωa + ωapa() t = κa NtEt () () dt dt 2 d Pa t 2

30 Coupling QM to EM at the rate constant level Nature Nano 8, (2013) Results: (1) Emission shows threshold behavior (2)Population inversion distribution show plasmon enhancement (3)Population inversion is pinned above the lasing threshold <50 nm from particles

31 New work shows that lasing can be tuned by changing dye/refractive index with liquid gain materials Laser emission: experiment experiment theory Laser emission: theory A. Yang, T. B. Hoang, C. Deeb, M. Dridi, M. Mikkelsen, GCS, T. Odom, Nature Comm., 6, 6939 (2015)

32 DNA-linked Nanoparticle Superlattices S. Y. Park, A. K. R. Lytton-Jean, B. Lee, S. Weigand, GCS, C. A. Mirkin, Nature, 451, 553 (2008).

33 What crystal lattices occur when particles have different sizes and DNA loadings? Geometrical model: lattice is determined by crystal that has the largest DNA hybridization # DNA/nanoparticle 2.55Å/bp 3.40Å/bp Calculate for loading on each particle, then take smaller value Science, 334, (2011)

34 Science, 334, (2011) NaCl Cr 3 Si CsCl FCC BCC AlB 2 Cs 6 C 60 Simple Cubic

35 DNA-linked nanoparticle superlattices: Extension to Nonspherical Particles M. Jones, R. MacFarlane, B. Lee, J. Zhang, K. Young, A. Senesi, C. Mirkin, Nat. Mat 9, 913 (2010). R, H, Macfarlane, B. Lee, M. R. Jones, N. Harris, G. C. Schatz, C. A. Mirkin, Science, 334, (2011).

36 Experimental Studies for Disks show Plasmon Hybridization and Fano Interference effects High energy anti-bonding mode Bonding mode with a net dipole M. O Brien, M. R. Jones, K. L. Kohlstedt, GCS and CAM, Nano Lett, 15, 1012 (2015)

37 For Au 3D superlattice material, effective medium approximation leads to red shifts in extinction spectra with increasing crystal size A. Lazarides and G. C. Schatz, J. Phys. Chem. 104, (2000) M. B. Ross, J. C. Ku, B. Lee, C. A. Mirkin and G. C. Schatz, J. Phys. Chem. C 120, (2016)

38 Silver Superlattices show collective metallic response Re ε Dielectric LSPR Metallic Kaylie L. Young, Michael B. Ross, Martin G. Blaber, Matthew Rycenga, Matthew R. Jones, Chuan Zhang, Andrew J. Senesi, George C. Schatz, and Chad A. Mirkin, Adv. Mat. 26, (2013). BCC: Ag 20 nm diameter 20 nm edge to edge 38

39 Ag superlattice aggregates: theory vs expt Metallic Dielectric red: 17.1% Ag green: 3.7% Ag blue: 1.5% Ag Kaylie L. Young, Michael B. Ross, Martin G. Blaber, Matthew Rycenga, Matthew R. Jones, Chuan Zhang, Andrew J. Senesi, George C. Schatz, and Chad A. Mirkin, Adv. Mater., 26, (2013).

40 DNA-linked nanoparticle superlattice crystals Auyeung, et al., Nature 2014, 505, 73. scale bar: 5 um

41 Plasmonic/Photonic Crystals made by DNA Nanoparticle Assembly Show Strong Coupling of Plasmons and Fabry-Perot Modes S P Volume Fraction ~1% Volume Fraction ~10% 60 0 Surface Plasmon Cavity Modes e ω g (Scale bar 1 μm ) Theory 2D slab (EMT) Theory 2D BCC slab (FDTD) Experiment Fabry-Perot Modes D. J. Park et al. Photonic Crystals Realized through DNA Programmable Assembly Proc. Natl. Aca. Sci., 2014, doi: /pnas

42 Ag/Au Alloy and Bimetallic Superlattice Thin Films M. Ross, J. Ku, B. Lee, C. A. Mirkin and G. C. Schatz, Adv. Mat., 28, 2790(2016) Atomic vs nanoscale alloying leads to different results: reflects charge transfer at the atomic level that doesn t occur for nanoparticles.

43 Ag/Au Alloy and Bimetallic Superlattice Thin Films M. Ross, J. Ku, B. Lee, C. A. Mirkin and G. C. Schatz, Adv. Mat., 28, 2790(2016) Silver on left Gold on left Reflectivity is asymmetric as a result of the combination of gradient with lossy material. Expt Theory

44 Magneto-Plasmonics Provide New Opportunities for Designing Light-Matter Interactions Magnetic thin film Magnetic materials provide asymmetric and magneto-responsive optical properties: Kerr Rotation Kerr Ellipticity Faraday Rotation Au Ag Plasmonic systems provide exquisitely tunable optical properties Combination: plasmonic sensitivity and optical control with magneto-responsive character

45 Model System: TMOKE in Co-Superlattice Thin Films Superlattice modulates intensity and phase of light reaching the magnetic layer Manifests as changes in: Overall reflectance of multilayer structure Enhancement and control of TMOKE response Unusual positive TMOKE parameter for metallic Ag superlattice Transverse Magneto Optical Kerr Effect Michael B. Ross, Marc R. Bourgeois, Chad A. Mirkin and George C. Schatz, J. Phys. Chem. Lett. 7, (2016).

46 Conclusions 1. Solutions of Maxwell s equations for isolated silver and gold nanoparticles accurately match observed extinction spectra. 2. Arrays of nanoparticles which satisfy Bragg scattering conditions lead to lattice plasmon modes with narrow lines that are of interest in subwavelength lasers. 3. 3D arrays with well defined crystal habits lead to interesting plasmonic Fabry-Perot modes. There are also unique metamaterials properties associated with these materials. 4. We have developed a FDTD-based approach to describe plasmonmediated exciton transport.