Biomedical Engineering Reference
In-Depth Information
π
spirals have significantly fewer convergents in our region of
interest. However, OAM peaks are still clearly observed at linear
combinations of the convergents despite the significant broadening
due to the imperfect experimental alignment.
It is worth mentioning that the measured values of OAM peaks
are fully explained on the basis of the analytical far-field diffraction
theory [51] reviewed in Section 11.3. In particular, peaks in the
measured OAM spectra are observed at numbers corresponding
to the Fibonacci sequence for the GA spiral and more generally,
as demonstrated by Figs. 11.14 and 11.15, peaks are observed
matching the theoretically predicted values based on the fractional
expansion theory of irrational spirals. A full list of analytically
calculated and experimentally measured FHD peak positions can be
found in Ref. [47].
These results demonstrate the ability to design and generate
structured light with extremely complex orbital patterns simulta-
neously carrying a large number of azimuthal values in the far-
field diffraction zone. Moreover, the reconstructed complex field
images(Fig.11.13)indicatethepresenceofalargenumberofoptical
vortices that result from wavediffraction in aperiodic Vogel spirals.
It is very interesting to speculate on the engineering of novel
light sources that could radiate such complex optical beams or
couple them into conventional fiber-based communication systems
to achieve greatly expanded spatial multiplexing capabilities. More-
over, information coding in higher dimensional azimuthal bases
could drastically expand the present capabilities of both classical
and quantum information systems [53].
The successful demonstration of the superposition of many
OAM modes in engineered Vogel spiral arrays of Au nanoparticles
provides novel exciting opportunities for singular optics that are of
interest also to secure optical communication, optical trapping, and
plasmonic sensingtechnology.
11.4 Outlook and Conclusion
In this chapter, we presented a comprehensive overview of our re-
centworkontheengineeringofstructuredlightcarryingOAMusing
