Near-field optical micromanipulation with cavity enhancedevanescent waves

Prepared by David Keng

Nov. 3, 2006

Peter J. Reece,a Veneranda Garcés-Chávez, and Kishan Dholakia

School of Physics and Astronomy, University of St Andrews, Saint Andrews, Fife KY16 9SS, Scotland,United Kingdom

Important things in this paper

• Near-field optical micromanipulation with cavity enhanced evanescent waves

• Near-field optical micromanipulation

• cavity enhanced evanescent waves

Near-field optical micromanipulation

• Optical guiding and/or trapping particle with evanescent waves

Near-field optical micromanipulation

• In this paper…1064 nm CW laser (4 W, IPG Yb doped fiber laser)

Velocity of 5 m polymer colloids at a BK7 glass-water interface… ~4 um/s1.8W focused to a 200um spot (without enhancement layer!)With enhancement layer… 22±2.7 um/s!!

1.8 W / (2 x 10-4m)2 = 4.5 x 107 W/m2 Theirs…0.005 W / (4 x 10-6m)2 = 3.1 x 108 W/m2 Inside MP3L tapered fiber

Conclusion for Near-field optical micromanipulation

• To guide a particle…particle trapped within E.W. above surface

• To trap a particle…two counter propagating waves

• Larger the particle size… easier to trapsmaller the Brownian motion (high drag)higher polarizability (stronger trapping

force)

• Should be able to perform on the tapered fiber…

H2O

Enhancement• “dielectric resonator”

Looks like this…

SF11SiO2

1000nmZrO2

127nm

1.754 1.45 1.97 1.33

Enhancement

• Light is launched into the 127nm layer

• 32 times of the incident intensity in the layer

• 25 times at the surface

• 5~10 times measured… v = 2~4 vs. 22