A New Optical Tweezers Technique Using a Holographic Crystal

Erge Edgu-Fry, Kristian Helmerson, Joseph Reiner and Rani Kishore

Physics Division, National Institute of Standards and Technology, Gaithersburg, MD


It has been shown previously that radiation pressure from a highly focused beam can be used to trap and manipulate objects in an aqueous media [1]. Over the past decade there have been several studies done by various groups to increase the ability of trapping many particles simultaneously by realizing several traps as opposed to a single trap. There are mainly two approaches that stand out in these studies. One group [2] uses the so called phase contrast method in conjunction with a liquid-crystal spatial light modulator. They have the ability to produce tens of traps. With this method one can adjust the power associated with each one of these traps. However their limitation is that these traps are confined to two dimensions. The second group [3] uses a similar type of spatial light modulator and has control of their traps in three dimensions, but they cannot adjust the power of each trap individually.

Our goal is to combine these two important aspects of multiple trapping, i.e., the ability to trap in three dimensions and the individual control of each trap’s position and power. We are in the process of implementing a holographic crystal spatial light modulator that is computer controlled to our existing optical tweezers [4] system. Details of our optical setup, computer control and various challenges that we are trying to overcome will be reported.


  1. A. Ashkin, Phys. Rev. Lett. 24, 156 (1970)
  2. R. Eriksen et al., Optics Lett. 27, 267 (2002)
  3. E. Dufresne et al., Rev. Sci. Instr. 72, 1810 (2001)
  4. S. Kulin et al., Langmuir 19, 8206 (2003)


Presenting Author:

Name: Erge Edgu-Fry
Division : Physics
Laboratory : Physics
Room and Building address : A163/221 
Mail Stop  : 8424
Telephone  : (301)975-8575
FAX  : (301)975-8272
email  : erge@nist.gov
Sigma Xi member?  No