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Optical Tweezing with Adaptive Optics Canada France Germany - Young Photonic Researchers – Munich, 2009. Shaun Bowman Supervisors - Dr. Colin Bradley, Dr. Rodolphe Conan Adaptive Optics Laboratory. The Adaptive Optics Laboratory – University of Victoria. Key equipment:. Lab facts:.

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optical tweezing with adaptive optics canada france germany young photonic researchers munich 2009

Optical Tweezing with Adaptive OpticsCanada France Germany - Young Photonic Researchers – Munich, 2009

Shaun Bowman

Supervisors - Dr. Colin Bradley, Dr. Rodolphe Conan

Adaptive Optics Laboratory

the adaptive optics laboratory university of victoria

The Adaptive Optics Laboratory – University of Victoria

Key equipment:

Lab facts:

  • Founded 1998
  • Dr. Colin Bradley, director
  • 2 post docs
  • 2 PhD candidates
  • 2 Masters students
  • Co-op student / interns
  • Contract professionals
  • Deformable mirrors: 1k, 64, 52, and 32 actuator
  • Steer mirrors
  • HASO Beam profiler
  • Zygo interferometer
  • Micro EDM mill
  • Optics room
the adaptive optics laboratory university of victoria1

The Adaptive Optics Laboratory – University of Victoria

Astronomy Collaboration

  • European Space Agency
  • ACURA
  • University of California
  • Thirty-Meter-Telescope Project
  • NRC Hertzberg Institute of Astrophysics
  • University of Toronto
  • Canada-France-Hawii Telescope
  • Caltech Astronomy
  • ... and a lot I don't know!
optical tweezers ray optics regime

Optical Tweezers – Ray optics regime

Light as a manipulator

  • Particle:
    • Index of refraction > medium
    • Diameter ~ 5x wavelength to 100um
optical tweezers force applicator dynomometer

Optical Tweezers – Force applicator / dynomometer

Gauging and applying forces

  • Overdamped 2nd order system
  • Brownian motion gives Stochastic forcing function
  • => Langevin equation
  • =>Use power spectral density of position to deduce stiffness
science case for optical tweezers

Science Case for Optical Tweezers

Force extension

  • Study of DNA uptake by bacteria
    • Observe uptake
    • Measure stall-force (7 – 40 pN typ.)

P. Johnson, Simon Fraser University, 2007

background on adaptive optics

Background on adaptive optics

Adaptive Optics using deformable mirrors

  • Wave description of light:
  • A(x,y) => Amplitude
  • ζ(x,y) => Phase
  • Wave at trap = F( wave at aperture or deformable mirror)

The mirrors shape DIRECTLY

describes the phase!

sensing phase wavefront sensor the eyes

Sensing phase, wavefront sensor – the eyes

Optical Tweezing

  • Need phase for closed-loop
  • Cant measure the phase
  • Can measure focal position
  • Tilted phase causes position shift
  • Can measure SLOPE of the phase
  • Shack-hartmann wavefront sensor
controlling phase deformable mirrors the hands

Controlling phase, deformable mirrors – the hands

IN

OUT

Deformable mirrors

  • Peizo:
    • 0.5 – 2 um stroke
    • > 1khz bandwidth
  • Voice coil
    • 5 – 100 um stroke
    • > 400hz bandwidth

DM SHAPE = -0.5 x IN shape

closed loop control the brains

Closed loop control – the brains

Closed loop controllers

  • Command new position
  • Generate new phase reference
  • Controller removes phase error
  • Particle moves to new location
  • Calibrate:
    • Phase vs mirror voltages
    • Trap position vs phase
  • Invert
uvic optical tweezer apperatus

Uvic Optical Tweezer Apperatus

Closed loop controllers

  • Command new position
  • Generate new phase reference
  • Controller removes phase error
  • Particle moves to new location
  • Calibrate:
    • Phase vs mirror voltages
    • Trap position vs phase
  • Invert
using particle position in wavefront controller

Using particle position in wavefront controller

Command position in real units

  • Particle detection by symeteric-phase-only-matched-filter (SPOMF) method
  • Known Tip/Tilts applied to relate wavefront and trap position
using particle position in wavefront controller2

Using particle position in wavefront controller

Demonstration

  • 20 mW optical power at objective
  • 15 um polystyrene bead
  • 30 x 30 um range of motion
  • 50 um max wavefront tilt
current work

Current work

after

DMM and

WFS beamsplitter

to

trap forming

Microscope

objective

2x2 lenslets

Calibration

collimating

lens

  • Stiffness as a function of trap position
  • 2x2 Traps controlled by one deformable mirror
thank you

Thank you

Questions?

Shaun Bowman

Adaptive Optics Laboratory

University of Victoria

BC, Canada

Ph: 1 250 721 8624

sbowman@engr.uvic.ca