Integrated optical tornadoes for efficient light harvesting Svetlana V. Boriskina, Selcuk Yerci & Gang Chen NanoEngineering group Department of Mechanical.

Integrated optical tornadoes for efficient light harvestingSvetlana V. Boriskina, Selcuk Yerci & Gang Chen

NanoEngineering groupDepartment of Mechanical Engineering

Massachusetts Institute of Technology

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Cat. F5 tornado (Manitoba, Canada, June 2007)

Image credit: Juri Hahhal

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Ray picture dominates conventional thinking about light propagation

Image credit: Teresa Matfield

A. Mavrokefalos et al, Nano Lett. 12, 2792-2796, 2012

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Light trapping schemes typically rely on constructive interference of light rays

scattering

J. VanCleave, Colors & Thin-Film Interference, John Wiley & Sons, Inc.

Atwater & Polman, Nature Mater. 2010

field enhancement

waveguiding

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There is another way: making use of destructive interference

‘Black holes are where God divided by zero’Steven Alexander Wright

phase vortex

= indefinite phasezero intensity ))((exp)(),( tit rrUrE

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There is another way: making use of destructive interference

‘Black holes are where God divided by zero’Steven Alexander Wright

= indefinite phasezero intensity

Credit: iStockphoto.com/David Ciemny

))((exp)(),( tit rrUrE

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There is another way: making use of destructive interference

‘Black holes are where God divided by zero’

flow vortex

Steven Alexander Wright

phase vortex

Optical energy flows in the direction of the phase change

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Hydrodynamic analogy of light trapping

S.V. Boriskina, “Plasmonics with a twist,” in Plasmonics in metal nanostructures: Theory & applications ( Shahbazyan & Stockman eds.) Springer, 2013

Image credit: Teresa Matfield Image credit: http://www.forestwander.com

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Hydrodynamic analogy of light flow

Maxwell’s equations:

t

t

ΕJH

HE

H

E

0

S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90, 2012

)()()()( rrrvr

)()()( rrvrv V

‘mass’ conservation:

momentum conservation:

Navier-Stokes-like equations:

(Madelung, 1926)

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Hydrodynamic analogy of light flow

Maxwell’s equations:

t

t

ΕJH

HE

H

E

0

S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90, 2012

convective term

)()()()( rrrvr

)()()( rrvrv V

‘mass’ conservation:

momentum conservation:

potential created by the light trapping structure

material loss or gain

Navier-Stokes-like equations:

2|)(|)()( rUrr I

)(rv

‘Photon fluid’ density:

‘Photon fluid’ velocity:

(Madelung, 1926)

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How are optical tornadoes generated?

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By colliding several light beams with appropriate phases …

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… or by strategically positioning obstacles in the light flow path

S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90, 2012

Zero intensity

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S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90 (2012)W. Ahn, S.V. Boriskina, et al, Nano Lett. 12, 219-227 (2012)

Example of a vortex-pinning nanostructure

50-nm radius Au nanoparticles

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S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90 (2012)W. Ahn, S.V. Boriskina, et al, Nano Lett. 12, 219-227 (2012)

Example of a vortex-pinning nanostructure

50-nm radius Au nanoparticles

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S.V. Boriskina & B.M. Reinhard, Nanoscale, 4, 76-90 (2012)W. Ahn, S.V. Boriskina, et al, Nano Lett. 12, 219-227 (2012)

Optical energy is circulating outside the metal volume!

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What is the origin of the strong field enhancement?

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Optical vortices generate local velocity fields

Tangential velocity ~1/r

r

)()()( rrvrv V

• compressible fluid• potential steady-

state flow• local convective

acceleration possible

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‘Photon fluid’ is convectively accelerated in the vortex velocity field…

)()()( rrvrv V

• compressible fluid• potential steady-

state flow• local convective

acceleration possible

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… and when threaded through nanoscale gaps, generates ‘hydraulic jumps’ - areas of high field intensity

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… and when threaded through nanoscale gaps, generates ‘hydraulic jumps’ - areas of high field intensity

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Vortex-pinning nanostructures are photonic analogs of turbopumps

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Optical vortices can be moved and ‘stretched’ by repositioning the obstacles

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Tunable or broadband light trapping possible

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Beyond light trapping …

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Nanoscale light switching

S.V. Boriskina & B.M. Reinhard, Opt. Express, vol. 19, no. 22, pp. 22305, 2011

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Nanoscale light switching

S.V. Boriskina & B.M. Reinhard, Opt. Express, vol. 19, no. 22, pp. 22305, 2011

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Nanoscale light switching

S.V. Boriskina & B.M. Reinhard, Opt. Express, vol. 19, no. 22, pp. 22305, 2011

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Nanoscale light switching

S.V. Boriskina & B.M. Reinhard, Opt. Express, vol. 19, no. 22, pp. 22305, 2011

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Nanoscale light switching

S.V. Boriskina & B.M. Reinhard, Opt. Express, vol. 19, no. 22, pp. 22305, 2011

HT2013-17406 ‘Surface Plasmon Enhanced Radiative Nanoscale Heat Transfer’ Thu, July 18, 3:58pm, Salon G

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Conclusions and outlook

• New way of trapping light by molding it into nanoscale vortices

• Higher field concentration than traditional schemes based on constructive interference

• Strong energy flow outside of the metal volume of nanoparticles – PV applications

• New way of designing light absorbers via the hydrodynamic analogy

Many thanks to

Prof. Gang Chen & MIT NanoEngineering group

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SOLID STATE SOLAR THERMAL ENERGY CONVERSION (S3TEC) CENTER

The audience