Page 215 - Principles and Applications of NanoMEMS Physics

204 Chapter 5

6dB/86nm were determined. The FDTD study concluded that by optimizing
particle geometry it should be possible to achieve energy trabsport at a
velocity of 0.1c (c is the speed of light).
The direct experimental evidence of energy transport a waveguide
consisting of linear arrays of 90 nm x 30 nm x 30 nm rod-shaped Ag
nanoparticles with an inter-particle spacing of 50 nm and having the long
axis of the rods oriented perpendicular to the propagation direction to
increase the near-field coupling was fabricated. To probe energy transport,
the fluorescence of Molecular Probes Fluorspheres F-8801, polystyrene
nanospheres with a diameter of 110 ± 8 nm , placed randomly along the
waveguide, see Fig. 5-9, was detected.

Intensity
Intensity
Intensity
Fiber
Fiber
Fiber
Dye
Dye
Dye
Laser
Laser
Laser
Light
Light
Light
Field
Field Nanoparticles
Field
Nanoparticles
Coupling
Coupling
Coupling
Far Field
Far Field
Far Field
Detection
Detection
Detection
Figure 5-9. Sketch of SP propagation detection along waveguide by fluorescent molecules.
(After [211].)
The procedure entailed excitation of the first particle in the waveguide by
coupling laser light at a wavelength of 570 nm, the single particle resonance
wavelength, via the tip of an optical fiber, and monitoring its propagation
down the guide by measuring the position-dependent intensity of the light
emitted by the fluorescent molecules. The presence of plasmon transport was
signaled by a broader full width at half maximum of the fluorescent nano
spheres when a scan is done along the waveguide than perpendicular to it.
The results of the experiment were a decay length of dB6 / 195 ± 28 nm ,
m
corresponding to an energy propagation distance of 5.0 µ .

5.3.3 Nanophotonic SP-Based Devices

While still in its infancy, a number of SP-based devices have been
proposed [221], [222]. For instance, Bozhevolnyi et al. [221] advanced SP-