Let  Nothing  slow  you  down:  op3cally  trapped    micropar3cles  in  liquid,  air  and  vacuum  

Kishan  Dholakia1,*  

Michael  Mazilu1,  Yoshihiko  Arita1,  Tom  VeFenburg1,  Juan  Aunon1  Alison  McDonald,  Derek  Craig  and  and  Ewan  Wright*  

1School  of  Physics  and  Astronomy,  University  of  St  Andrews,  Fife,  Scotland  UK  *College  of  Op3cal  Sciences,  The  University  of  Arizona,  1630  East  University  

Boulevard,  Tuscon,  Arizona  85721-­‐0094,  USA  

Let  Nothing  slow  you  down:  op3cally  trapped    micropar3cles  in  liquid,  air  and  vacuum  

Kishan  Dholakia1,*  

Michael  Mazilu1,  Yoshihiko  Arita1,  Tom  VeFenburg1,  Juan  Aunon1  Alison  McDonald,  Derek  Craig  and  and  Ewan  Wright*  

1School  of  Physics  and  Astronomy,  University  of  St  Andrews,  Fife,  Scotland  UK  *College  of  Op3cal  Sciences,  The  University  of  Arizona,  1630  East  University  

Boulevard,  Tuscon,  Arizona  85721-­‐0094,  USA  

Gaussian (top) Airy (lower) Living zebrafish neural network Nature Methods 11, 541 (2014); Biomedical Optics Express 10, 3435(2014)

10 µm

Shaped Light: fundamentals, biophysics, light-matter

Nature Photonics 5, 335 (2011)

SINGLE BEAM GRADIENT TRAP: Ashkin et al, Opt Lett 11, 288 (1986)

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Fgradient ∝ α∇I

This talk: Angular momentum transfer to trapped particles in air and vacuum

Light for manipulation: Optical Tweezers

video jointly with I Poberaj group

New Directions in Optical Manipulation

Shaping light Material property of probe

Anti-Reflection coated particles

AR particle data take through equipartition and power spectrum analysis: k ~ 2-5x higher

Coating can be calculated but close to geometrical mean between titania and water

Hu Y., Nieminen, T. A., Heckenberg, N. R. & Rubinsztein-Dunlop, H. Antireflection coating for improved optical trapping. J. Appl. Phys. 103, 093119 (2008).

lħ per photon

±ħ per photon

Transfer of spin angular momentum

€

Ωspin ∝1 rlΩorbital ∝1 rl

3

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I ∝ P (2πλrl ) Vt ∝ lP rl2 Tl ∝ rl

3 lP

Transfer of orbital angular momentum

L. Allen et al., PRA 45, 8185 (1992)

Manipula3on  in  air/vacuum:  linear  and  rota3onal  effects  

•  Overdamped  to  an  underdamped  oscillator  –  New  forms  of  cavity  

optomechanics  and  nanophotonics  

•  Classical-­‐quantum  boundary    –  Quantum  ground  state  with  

mesoscopic  par7cles,  (quantum  fric7on)  

•  New  areas  of  study  –  gas  viscosity/

thermodynamics  

–  ultra  high  Q  sensors   Spin-­‐stabilised  satellite  

Optical Trapping in vacuum – an emergent area?

12  

Mo3va3on  for  rota3ng  par3cles  –  e.g.  vacuum  fric3on  

•  Quantum  fluctua7ons  induce  surface  charges  

•  Van  der  Waals  force  of  aFrac7on  •  Image  charges  ‘lag’:  noncontact  fric7onal  component  

Figure adapted from: Pendry J B, Quantum friction- fact or fiction?, New J. Phys.,(2010)

Photo  diode  

Circularly  polarised  (CP)    trapping  beam  (1070nm)  

Vacuum  chamber  

Experiment:  trap  and  rotate  in  air  or  vacuum  

Vaterite  crystal  d  =  4.4µm  

x  

z  

Ωrot   Ωxy  

Ωz  

Birefringent  

ω1  

ω2  =  ω1  ±  2Ωrot  

ω1  

CP  

Can levitate Si particles in a similar way

Par3cle  dynamics  in  vacuum  

frot  =  Ωrot/2π  fxy  =  Ωxy/2π  fz  =  Ωz/2π  

2frot  

frot  fxy  

fz  

       Rota3on  versus  pressure  for  the  microgyroscope  

d  >  mfp  d  <  mfp  

frot  =  Ωrot/2π  

a  ≈  109g  m/s2  

d:  par3cle  diameter  mfp:  mean  free  path  

Arita et al. Nature Comm 4, 2374 (2013)

Optical torque Principal moments of inertia

Angular velocity in the body frame

Optical torque in the body frame

Rotation operator

Anisotropic polarisability tensor

Rotational stabilization

Op3cal  Euler  equa3ons  

Fusilli  

Par3cle  effec3ve-­‐temperature  by  equipar33on  theorem  

Lateral  x-­‐y  mo3on   Axial  z  mo3on  

Langevin  equa7ons  Position power spectrum

Translation & rotation

Rotational stabilisation

Parameters  to  consider  for  a  SiO2  micropar3cle  in  an  LG  beam  

mg  

FscaF  

Fcentripetal  

FscaF  α  l  

R  α  l  €

F ∝∇IDynamics  is  an  interplay  between  all  of  these  forces  

Acknowledgements

Michael Mazilu Yoshihiko Arita Juan Aunon Tom Vettenburg Alison McDonald Derek Craig

Collaborators Ewan Wright, Tucson, Arizona Halina Rubinsztein-Dunlop, Queensland, Australia

Visit us at http://photon.st-andrews.ac.uk/manipulation/ (new postdoc and PhD positions..please ask!)