The Exciting Science of Light with Metamaterials

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1 And The Exciting Science of Light with Metamaterials Vladimir M. Shalaev Birck Nanotechnology Center

2 Outline Intro to metamaterials Nanophotonics enabled by Plasmonics and Metamaterials Toward Better Materials for MM and TO applications Negativeindex metamaterials Transformation optics and cloaking Engineering PDOS & Subwavelength light confinement with Hyperbolic MMs Flat photonics with Metasurfaces: Generalized Snell s Law, negative refraction, metalens, metahologram.

3 Natural Optical Materials E,H ~exp[in(ω/c)z] n = ± (εμ) Air Water metals Crystals Electrical Plasma (Metals at optical wavelengths) Evanescent waves k 1 Common Transparent Dielectrics H E S k Semiconductors k S E H Negative Index Materials 1 k Evanescent waves Magnetic Plasma (Not naturally occurring at optical wavelengths)

4 What is a metamaterial? Metamaterial is an arrangement of artificial structural elements, designed to achieve advantageous and unusual electromagnetic properties. ta = meta = beyond (Greek) A natural material with its atoms A metamaterial with artificially structured atoms

5 Photonic crystals vs. Optical metamaterials: connections and differences 0 1 a a<<. Effective medium description using Maxwell equations with,, n, Z Example: Optical crystals Metamaterials a~ Structure dominates. Properties determined by diffraction and interference Example: Photonics crystals Phased array radar Xray diffraction optics a>> Properties described using geometrical optics and ray tracing Example: Lens system Shadows

$natural have properties governed by the diffraction of the periodic structures may$

6 Photonic crystals... have lattice constants comparable to light wavelengths: a ~ can be artificial or natural have properties governed by the diffraction of the periodic structures may exhibit a bandgap for photons typically are not well described using effective parameters,, n, Z often behave like but they are not true metamaterials

7 Electrical Metamaterials (Plasmonics): Route to Nanophotonics

8 Operating speed Why Plasmonics/Electric MMs? PHz THz Metallic Nanoplasmonics Dielectric Photonics GHz MHz khz Semiconductor Electronics The past 10nm 100nm 1m 10m 1mm 100m Critical dimension active devices (nm) Plasmonics will enable an improved synergy between electronic and photonic devices Plasmonics naturally interfaces with similar size electronic components Plasmonics naturally interfaces with similar operating speed photonic networks M. Brongersma, V. Shalaev, Science (2010)

9 Silicon Integrated Nanophotonics

BLUE optical waveguides and YELLOW copper wires After More Than a Decade of Research, Silicon

10 IBM Silicon Integrated NP Technology IBM 90nm Silicon Integrated Nanophotonics: Integrated photodetector (red feature) Modulator (blue feature) Silicon transistors (red sparks) IBM chip: BLUE optical waveguides and YELLOW copper wires After More Than a Decade of Research, Silicon Nanophotonics is Ready for Development of Commercial Applications. IBM Press release, December 10, 2012

ELECTRONICPHOTONIC INTEGRATION: SUMMARY Modern communication systems Huge amount of data Ever increasing speed Electronic circuit Very compact (~ 10nm) Operational speed is limited (RCdelay) Photonic

11 ELECTRONICPHOTONIC INTEGRATION: SUMMARY Modern communication systems Huge amount of data Ever increasing speed Electronic circuit Very compact (~ 10nm) Operational speed is limited (RCdelay) Photonic circuit High speed High bandwidth Component size is limited (>~ 100nm 1 µm) Diffraction limit Optical mode in waveguide > 0 /2n CORE Electronic Photonic circuit: NEED FOR NEW TECHNOLOGIES Si NANOPHONICS (nearterm) PLASMONICS/METAMATERIALS (~5 years)

12 OPTICAL NANOANTENNAE OE (2009); NJP (2008); Metamaterials (2008); APL (2008) [ Bowtie antennas ] from LCcontour to nanophotonic circuits (Engheta metatronics ) Other Applications: Sensors

Optical Nanolaser Enabled by SPASER Related

Shalaev, Wiesner groups, Nature (2009) Zhang

Laser Zheludev, Stockman M. T. Hill, et al; C. Z. Ning, et al (electr.

13 Optical Nanolaser Enabled by SPASER Related prior theory: Stockman (SPASER) Noginov, Shalaev, Wiesner groups, Nature (2009) Zhang group: Plasmon Laser (Nature,2009) RoomT Plasmon Laser (Nat. Mat, 2010) Optical MOSFET (Stockman) Spasing Laser Zheludev, Stockman M. T. Hill, et al; C. Z. Ning, et al (electr. pump) Spotlight on Plasmon Lasers (Perspective, Science, 2011) X. Zhang, et al

14 Toward Better Materials for Plasmonic and MM Applications (Boltasseva group, Purdue)

15 New Plasmonic Materials METALS TO LESSMETALS: Doped semiconductors Intermetallics (nitrides, borides, silicides, ) A. Boltasseva and H.A. Atwater, Science 331 (2011)

16 Alternative Plasmonic Materials Transparent Conductive Oxides ε becomes negative below 2μm P. West, et al, Lasers & Photon. Rev. (2010) (Boltasseva group) (see also work by the Noginov group)

Titanium Nitride Metallic: Golden luster Researchers Discover

May Merge Photonic and Electronic Technologies Hard & tough:

release March 27, 2012 http://www.minilathe.

17 Titanium Nitride Metallic: Golden luster Researchers Discover a New Path for Light Through Metal: Novel Plasmonic Material May Merge Photonic and Electronic Technologies Hard & tough: high speed drillbits Wellestablished processing OSA press release March 27, G.V. Naik et al., Optical Materials Express 2 p. 478 (2012)

18 New Plasmonic Materials for HMMs Performance of HMM devices: (A. Hoffman, Nature Materials 6(2007) ) FOM=Re{k }/Im{k } G..V. Naik and A. Boltasseva, Metamaterials 5(2011) 17 Phys. Status Solidi RRL 4, 295 (2010)

19 Negative Refraction in allsemiconductor based HMM G. Naik, et al, PNAS (2012)

$Negative refraction in semiconductorbased metamaterials Semiconductors exhibit metallic properties when heavily doped Aluminum doped zinc oxide (AZO) exhibits metallic property in the nearinfrared$

20 Negative refraction in semiconductorbased metamaterials Semiconductors exhibit metallic properties when heavily doped Aluminum doped zinc oxide (AZO) exhibits metallic property in the nearinfrared Conventional metals replaced by semiconductorbased ones such as AZO can produce high performance metamaterials The figureofmerit of AZO/ZnO metamaterial is 11: three orders higher than metalbased designs G. Naik, et al. PNAS (2012) (Boltasseva /Shalaev groups)

21 21

22 energy can be carried forward at the group

$Sir Horace Lamb Negative refraction and backward$ propagation of waves Mandel stam, 1945 Lefthanded

simultaneously negative values of and Veselago, 1968

Agranovich, Pendry, the one who whipped up the recent

22 22 energy can be carried forward at the group velocity but in a direction that is antiparallel to the phase velocity Schuster, 1904 Sir Arthur Schuster Sir Horace Lamb Negative refraction and backward propagation of waves Mandel stam, 1945 Lefthanded materials: the electrodynamics of substances with simultaneously negative values of and Veselago, 1968 L. I. Mandel stam V. G. Veselago Others: Sivukhin. Agranovich, Pendry, the one who whipped up the recent boom of NIM researches Perfect lens (2000) EM cloaking (2006) Sir John Pendry

$23 Refraction: n 2$ Figure of merit: F

23 23 Refraction: n 2 εμ n εμ θ 2 θ 1 Figure of merit: F n' / n" n 0, if ' ' 0 θ 1 θ 2

24 24 S. Zhang, et al., PRL (2005) Dielectric Metal H E k Nanostrip pair (TM) < 0 (resonant) Nanostrip pair (TE) < 0 (nonresonant) Fishnet and < 0

25 Negative Refraction Effects O. Hess, Nature 455, 299 (2008)

26 Negative Refraction Effects

27 V. M. Shalaev, Transforming Light, Science, Oct. 17,

28 28 Fermat: δ ndl = 0 n = ε(r)μ(r) curving optical space Straight field line in Cartesian coordinate Distorted field line in distorted coordinate Spatial profile of & tensors determines the distortion of coordinates Pendry et al., Science, 2006 Leonhard, Science, 2006 Greenleaf et al (2003) L. S. Dolin, Izv. VUZ, Seeking for profile of & to make light avoid particular region in space optical cloaking

29 Forminvariance of Maxwell s equations Coordinate transformation from x to coordinate x is described using the Jacobian matrix G: g x x ij i j Maxwell s equation in x ( E) ( H ) 0 E H t H E t J Transformation of variables GG G T ; GG G T 1 T 1 E ( G ) E; H ( G ) H GJ J ; G G T Ward and Pendry, J. Mod.Opt. 43, 777 (1996)

$refractive index in a desert mirage Pendry et al.$

30 The bending of light due to the gradient in refractive index in a desert mirage Pendry et al., 2006

31 Kildishev, VMS (OL, 2008); Shalaev, Science

Zhang group) Light concentrator (also, Schurig

31 31 Kildishev, VMS (OL, 2008); Shalaev, Science 322, 384 (2008) (b) Fermat: δ ndl = 0 n = ε(r)μ(r) curving optical space Planar hyperlens (Kildishev and VMS) (Schurig et al; Zhang group) Light concentrator (also, Schurig et al) Optical Black Hole (Zhang group; Narimanov,Kildishev)

32 32 Narimanov, Kildishev

33 Invisibility in Nature, Physics and Technology Natural camouflage Black hole Current technologies to achieve invisibility: Stealth technique: Radar crosssection reductions by absorbing paint / nonmetallic frame / shape effect Optical camouflage: Projecting background image onto masked object. F117 Nighthawk Stealth Fighter Optical Camouflage, Tachi Lab, U. of Tokyo, Japan

34 Examples with scientific elements: The Invisible Man by H. G.

$.. to lower the refractive index of a substance, solid or liquid, to that of air so far as all$ .. she achieves these feats by bending all wavelengths of light in the vicinity around herself.

.. she achieves these feats by bending all wavelengths of light in the vicinity around herself.

34 34 Examples with scientific elements: The Invisible Man by H. G. Wells (1897) The invisible woman in The Fantastic 4 by Lee & Kirby (1961) "... it was an idea... to lower the refractive index of a substance, solid or liquid, to that of air so far as all practical purposes are concerned. Chapter 19 "Certain First Principles" "... she achieves these feats by bending all wavelengths of light in the vicinity around herself... without causing any visible distortion. Introduction from Wikipedia Pendry et al.; Leonhard, Science, 2006 (Earlier work: cloak of thermal conductivity by Greenleaf et al., 2003)

35 Optical Cloaking with Metamaterials: Can Objects be Invisible in the Visible? Nature Photonics (to be published) Cover article of Nature Photonics (April, 2007)

36 Unit cell: Flexible control of r ; Negligible perturbation in metal needles embedded in dielectric host Cai, et al., Nature Photonics, 1, 224 (2007)

37 Cloaking performance: Field mapping movies Example: 632.8nm with silver wires in silica Cloak OFF Cloak ON

38 picture from discovery.com J. Li and J. B. Pendry, Phys. Rev. Lett., 2008

39 39 Progress Towards True Invisibility on May.17, 2009, under Science Theory: J. Li, J. Pendry GHz: Smith et al (Duke) Optical: Zhang et al (Berkeley) Lipson et al (Cornel)

fcontrol C Signal Control C (c) Wave guide A B C Control A Signal Control C (d)

40 Turn on Control A Control A Signal Control C (a) Wave guide A B C Control A Signal Control C (b) Wave guide A B C Star Trek transporter Control A Turn of fcontrol C Signal Control C (c) Wave guide A B C Control A Signal Control C (d) Wave guide A B C M. W. McCall and et al., Journal of Optics, 2011 Gaeta eta al, experiment

Modern cosmology describes Universe as collection of

These spaces may have different topology and

Using transformation optics we can create optical

normally fit into Euclidean 3D space: Even metric

2010): 2 2 2 2 2 2 1 2 2 2 2 1 y x z t c 0 1 2 0 0 2

41 Modern cosmology describes Universe as collection of spaces connected by black holes and wormholes. These spaces may have different topology and different number of dimensions. Using transformation optics we can create optical spaces having nontrivial topology, which cannot normally fit into Euclidean 3D space: Even metric signature of the optical space may differ from the ( ) signature of the Minkowski space. In hyperbolic materials (Smolyaninov, Narimanov PRL, 2010): y x z t c x x x x Flashes of light are observed during metric signature transitions : toy Big Bang physics 2T KG 41

42 Hyperbolic Metamaterials: Engineering Photonic Density of States & Subwavelength Light Confinement S. Ishii, et al, Laser Photonics Rev., 1 7 (2013) DOI /lpor

43 Cover article

44 Hyperbolic Metamaterials (HMMs) A metamaterial has hyperbolic dispersion relation normal dispersion kx ky kz c 2 hyperbolic dispersion k k k c x y z 2 z y kx ky kz c 2 z y x Jacob, et al., Opt. Express, 2006 x Transverse Positive (TP) Transverse Negative (TN)

45 PHOTONIC DENSITY OF STATES (PDOS) Isofrequency surface at ωδω Isofrequency surface at ω

QED IN THE HYPERSPACE Fermi s Golden Rule: (Dipole matrix element) 2 Available density of states for emitted light Coupling of emitter to field (depends on the mode volume) Rate of SE,

46 QED IN THE HYPERSPACE Fermi s Golden Rule: (Dipole matrix element) 2 Available density of states for emitted light Coupling of emitter to field (depends on the mode volume) Rate of SE, can be understood as property of atomenvironment system Environment (cavity, PhC, nanowire) enhances density of states Environment strongly alters the rate of SE through the available PDOS!

47 EMISSION POWER SPECTRUM Calculation Methods: : Ford and Weber (1984) QED: Hughes group (2009)

$Diffraction inside Hyperbolic Media Hyperbolic metamaterial (HMM) Ag/SiO 2 lamellar HMM =465 nm =465 nm eff x eff z 2.78 0.22i 6.310.$

48 Diffraction inside Hyperbolic Media Hyperbolic metamaterial (HMM) Ag/SiO 2 lamellar HMM =465 nm =465 nm eff x eff z i i S (15 nm Ag/15 nm SiO 2 ) 3 Highk waves are supported Propagation of highk waves is confined Diffraction from double slits FWHM = 45 nm at = 465 nm S. Thongrattanasiri and V. A. Podolskiy, Opt. Lett. (2009) Satoshi Ishii et al, in preparation

49 Subwavelength Interference (Experiment) 1. Sample fabrication Deposition and FIB 2. Photolithography Photoresist exposure, develop 3. AFM scan =465 nm For Ag/SiO 2 HMM sample: FWHM = 83 nm (< ) For SiO 2 sample: FWHM = 542 nm (~ ) Ag/SiO 2 HMM sample SiO 2 sample

50 Flat Photonics with Metasurfaces: Generalized Snell s Law, Negative Refraction, and much more... Birck Nanotechnology Center

51 Principle of Least Action Maupertuis felt that Nature is thrifty in all its actions, and applied the principle broadly Pierre Louis Maupertuis ( ) Leonhard Euler ( ) Louis de Broglie ( )

$ФdФ n t θ t For reflection B For refraction In essence, momentum conservation! see also S. Larouche and D.R. Smith, OL v. 37, 2391 (2012)$

52 Generalized Snell s Law (Capasso Group) A Principle of least action The momenta difference between blue and red path is zero θ r n i dr Ф ФdФ n t θ t For reflection B For refraction In essence, momentum conservation! see also S. Larouche and D.R. Smith, OL v. 37, 2391 (2012)

53 Generalized Snell s Law Demonstrated at 8 µm wavelength N. Yu, et al. Science, 2011 (Capasso Group)

54 Broadband light bending with plasmonic nanoantennas unit: nm z y Λ Λ/8 x X. Ni, et al. ScienceExpress, Dec. 22, 2011 (Shalaev & Boltasseva groups) Science v. 335, 427 (2012)

55 Incident Angle Sweep Refraction λ = 1500 nm

56 Incident Angle Sweep Reflection λ = 1500 nm

57 Broadband Negative Refraction Broadband! θ i = 30⁰

58 Ultrathin planar metalenses: design r Au film (30 nm) by electron beam evaporation Babinet antennas fabrication by focused ion beam (FIB) X. Ni etal (2012)

59 Ultrathin planar metalenses: experiment Focal length: 2.5 μm Focal length: 4 μm Focal length: 7 μm ypolarizer sample xpolarizer Ar/Kr laser (676 nm / 530 nm / 476 nm) Z = 0 μm Z = 7 μm Z = 10 μm wavelength 676 nm

60 Take home messages Nanophotonics enabled by Plasmonics and Metamaterials Toward Better Materials for MM and TO applications Negativeindex metamaterials Transformation optics and cloaking Engineering PDOS & Subwavelength light confinement with Hyperbolic MMs Flat photonics with Metasurfaces: Generalized Snell s Law, negative refraction, metalens, metahologram.

Transforming Light with Metamaterials

Transforming Light with Metamaterials Vladimir M. Shalaev Birck Nanotechnology Center Outline Electrical Metamaterials (Plasmonics): A Route to Nanophotonics Artificial Optical Magnetism in Metamaterials