118
I. Falcón Casas and W. Kautek
Fig. 3.5 Normalized E 2 intensity field distribution along x-direction on sample surface underneath
the tip as a function of laser incident angle θ. The maximum intensity is about 333 at θ = 30 ◦ .
Reprinted from [44] with permission of Springer
Fig. 3.6 Field enhancement for bottom and top illumination for several metallic tip and wire radii.
A radially polarized laser beam is focused by a parabolic mirror on a metallic cylindrical wire. The
wire has a diameter ρ, ending with a tapered conical tip. Reprinted from [46] with permission of
The Optical Society
materials. Plasmon resonances are dominant in the visible region, while lightning
rod and antenna effects seem to play a stronger role for longer wavelengths.
The tip radius also affects field enhancement related with the lightning rod effect.
A smaller tip radius causes a higher surface charge accumulation leading to a
stronger near-field enhancement. Various simulations show that the enhancement
factor increases exponentially with the reciprocal of the tip radius [36, 41, 46, 50,
58]. Few studies exist on the influence of the laser spot size [46, 59].
I. Falcón Casas and W. Kautek
Fig. 3.5 Normalized E 2 intensity field distribution along x-direction on sample surface underneath
the tip as a function of laser incident angle θ. The maximum intensity is about 333 at θ = 30 ◦ .
Reprinted from [44] with permission of Springer
Fig. 3.6 Field enhancement for bottom and top illumination for several metallic tip and wire radii.
A radially polarized laser beam is focused by a parabolic mirror on a metallic cylindrical wire. The
wire has a diameter ρ, ending with a tapered conical tip. Reprinted from [46] with permission of
The Optical Society
materials. Plasmon resonances are dominant in the visible region, while lightning
rod and antenna effects seem to play a stronger role for longer wavelengths.
The tip radius also affects field enhancement related with the lightning rod effect.
A smaller tip radius causes a higher surface charge accumulation leading to a
stronger near-field enhancement. Various simulations show that the enhancement
factor increases exponentially with the reciprocal of the tip radius [36, 41, 46, 50,
58]. Few studies exist on the influence of the laser spot size [46, 59].