Transcript Near-field optical micromanipulation

Near-field optical micromanipulation with cavity enhanced
evanescent waves
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
Prepared by David Keng
Nov. 3, 2006
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/s
1.8W focused to a 200um spot (without enhancement layer!)
With enhancement layer… 22±2.7 um/s!!
1.8 W / (2 x 10-4m)2
0.005 W / (4 x 10-6m)2
= 4.5 x 107 W/m2
= 3.1 x 108 W/m2
Theirs…
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 trap
smaller the Brownian motion (high drag)
higher polarizability (stronger trapping force)
• Should be able to perform on the tapered fiber…
Enhancement
• “dielectric resonator”
Looks like this…
SF11
1.754
SiO2
ZrO2
H2O
1000nm 127nm
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