Optical Tweezers for Biological Manipulation using Cylindrical Vector Beams

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Optical Tweezers for Biological Manipulation
using Cylindrical Vector Beams

• By
• Yen Chin Woo
• Advisor
• Professor James Leger
• Spring 2004

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Summary

• Introduction to optical tweezers
• Development of individual systems
• White light Imaging
• Laser construction
• Integration of laser and white light optical
  systems
• Preparation of polystyrene spheres
• Future work
• Budget

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What is Optical Tweezers?

• Tool for manipulating microscopic biological
  objects, such as cells and bacteria.
• For focused light beam, the intensity maximum
  occurs at the focus, so the particles will be
  attracted to the focus.
• Many areas of applications
• Biology
• Genetics
• Neuroscience
• Molecular Medicine
• Pharmacy
• Biotechnology
• Reproductive Medicine

A simple Optical Tweezers
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New Design of Optical Tweezers

• Systems
• White light Imaging
• NdYAG laser
• Laser/white light optical system
• Polarization system
• Tweezers can trap and hold small particles with
  different refractive indices by changing the beam
  shape

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Testing of White Light Imaging System

• White light imaging is used to locate an observed
  sample
• System consists of fiber illuminator, camera, and
  objective
• This optical system will be merged with high
  power laser to control laser

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Laser design and construction
Laser Diagram
Resonator Stability Diagram

• Stable if
• Choose d 45 cm
• Mode size

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Testing of NdYAG Laser beam
(i) Multiple spatial mode
(ii) Tem00

• Multiple mode
• Design to ensure fundamental oscillation
• Measurements of power (Output coupler mirror 3
  Watts, End mirror 50 mW)

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Integration of YAG and white light optical
systems

• The laser beam must be made collinear with the
  white light imaging system
• Laser beam must be able to scan.
• Laser power must be adjusted for optimum
  performance.

Superposition of white light image
and laser beam
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Preparation of Polystyrene Spheres
(i) 4.5um spheres without added water

• New optical system was built
• Imaged and measured polystyrene spheres
• Measured spheres were within 10 of the
  theoretical value
• Added water to dilute or disperse spheres
• The cohesive force tends to make the particle
  stick together
• Different experiment taken to get the proper
  solution

(ii) Added water to dilute 4.5um spheres
4.17um
(iii) Added water to dilute 6.0um spheres
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Focus shaping using cylindrical vector beams

• The linearly superposition of radially polarized
  and azimuthally polarized components is a
  generalized cylindrical vector beam.
• Different polarization results in different
  focused spot shape

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Timeline
Sept Oct Nov Dec Jan
Feb Mar April May
Past
Current
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Budget
The estimated costs for the project are listed

• Past Budget
• 0 Printing and photocopying are covered by HKN
  and the UMN Electrical Engineering Department
• 200 Polystyrene spheres
• 0 Research resources will be provided by
  Professor Leger
• Total 200

• Current Budget
• 0 Printing and photocopying are covered by HKN
  and the UMN Electrical Engineering Department
• 180 Polystyrene spheres
• 120 Microscopic objective
• Total 300

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Summary

• Development of individual systems
• White light Imaging
• Laser construction
• Integration of laser and white light optical
  systems
• Preparation of polystyrene spheres
• Timeline
• Budget

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Thank you for Listening!