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Optical Tweezing with Adaptive Optics Canada France Germany - Young Photonic Researchers – Munich, 2009 Shaun Bowman Supervisors - Dr. Colin Bradley, Dr.

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Presentation on theme: "Optical Tweezing with Adaptive Optics Canada France Germany - Young Photonic Researchers – Munich, 2009 Shaun Bowman Supervisors - Dr. Colin Bradley, Dr."— Presentation transcript:

1 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

2 The Adaptive Optics Laboratory – University of Victoria Lab facts: Founded 1998 Dr. Colin Bradley, director 2 post docs 2 PhD candidates 2 Masters students Co-op student / interns Contract professionals Key equipment: Deformable mirrors: 1k, 64, 52, and 32 actuator Steer mirrors HASO Beam profiler Zygo interferometer Micro EDM mill Optics room

3 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!

4 Optical Tweezers – Ray optics regime Light as a manipulator Particle: Index of refraction > medium Diameter ~ 5x wavelength to 100um

5 Optical Tweezers – Force applicator / dynomometer Gauging and applying forces Overdamped 2 nd order system Brownian motion gives Stochastic forcing function => Langevin equation =>Use power spectral density of position to deduce stiffness

6 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

7 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!

8 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

9 Controlling phase, deformable mirrors – the hands 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 IN OUT

10 Closed loop control – the brains Closed loop controllers Calibrate: Phase vs mirror voltages Trap position vs phase Invert Command new position Generate new phase reference Controller removes phase error Particle moves to new location

11 Uvic Optical Tweezer Apperatus Closed loop controllers Calibrate: Phase vs mirror voltages Trap position vs phase Invert Command new position Generate new phase reference Controller removes phase error Particle moves to new location

12 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

13 Using particle position in wavefront controller Modified controller

14 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

15 Current work Calibration Stiffness as a function of trap position 2x2 Traps controlled by one deformable mirror to trap forming Microscope objective after DMM and WFS beamsplitter 2x2 lenslets collimating lens

16 Thank you Questions? Shaun Bowman Adaptive Optics Laboratory University of Victoria BC, Canada Ph:


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