A particle can be trapped at the focus of a laser beam. In our lab we are trying to extend this technique to handle wider range of objects.

Experimental Result

A 10 micron polystyrene particle (circled) was trapped and was moved to another location. The image before (top) and after (bottom) the translation are shown. The images are inverted.

Principle of the optical tweezer

A ray of light changes its direction after  passing through the object. The diffrence in the momentum before and after passing through the objcetct

References

1) A. Ashkin: “Acceleration and Trapping of Particles by Radiation Pressure,” Phys. Rev. Lett., 24 (1970) 156-159 

2) 岡村秀樹:”分子光学—高強度レーザー光による分子の運動制御とその応用—“, 分光研究, 50 (2001) 101-109,