Biomedical Engineering Reference
In-Depth Information
Figure 11.13
(a) Optical set up used for the complex amplitude retrieval.
(b,c) Analytically calculated phase portrait of far-field radiation from GA
and
spirals, respectively. (d,e) Experimentally measured phase portrait
from GA and
μ
spirals, respectively. Shaded areas indicate regions where
the field intensity is too low tomeasure thephase accurately. These regions
are ignored in the FHD. Reproduced from Ref. [51], with permission of the
Optical Society.
μ
scattered radiation from GA and
μ
spirals is shown in Fig. 11.13b,c,
respectively. The measured phase from the GA spiral is shown in
Fig. 11.13d and the phase from a
μ
spiral is shown in Fig. 11.13e.
The shaded areas in Fig. 11.13 indicate the limits (angular range)
where the measurement of the scattered light is inaccurate due to
the limitations of the experimental setup [47]. Very similar results
were obtained for the
μ
and
π
spirals (not shown here). The insets
in the reconstructed phase portraits in Fig. 11.13 highlight the
formation of a distribution of optical vortices at positions that well
match the analytical calculations.
Modal decomposition was used to analyze a superposition of
OAM carrying modes in the far-field pattern and determine their
relative contribution [64]. Decomposition into a basis set with
