Biomedical Engineering Reference
In-Depth Information
Figure 10.14
Two-dimensional5
×
6microneedlearrayfabricatedbyusing
OV pulses. Reprinted from Ref. [16] with permission of the Optical Society,
Copyright 2010.
structures, such as needles. The formation of the nanoneedle
requires the collection and confinement of the melted metal to an
on-axis hole of the OV by the photon pressure. In Gaussian beams
that do not have an on-axis hole, the collection of the melted metal
does not occur e
ciently.
10.3.2
Chiral Nanoneedle Fabrication
There is no known technique to twist material on a nanoscale.
In particular, it is impossible to twist metal on a nanoscale to
create spiral (chiral) metal nanoneedles, even by utilizing advanced
chemical techniques. Laser materials processing breaks down a
metal into its constituent elements (melted or vaporized metal) by
high-intensity laser pulses, and it is unsuitable for recombining the
constituent elements and structuring spiral materials. Therefore,
lasermaterialsprocessinghasnotbeenperformedtoproducechiral
metal nanoneedles.
As mentioned above, optical vortices have a wavefront helic-
ity due to a phase singularity, and they carry orbital angular
momentum,
l
. Circularly polarized light also has a polarization
