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9 years ago This issue was discussed at TaCoNa Photonics 2012, see
http://dx.doi.org/10.1063/1.4750091
http://dx.doi.org/10.1063/1.4750119
Overall, ADDA is ready for such simulations using '-beam read ...'. Any
singular field (e.g. general multipole) can be used, as long as the singularity
is outside of the scatterer (nanoparticle). The internal fields produced by
ADDA will be correct, but cross sections are not exactly what one might expect.
Absorption cross section is the correct one, i.e. it exactly corresponds to the
non-radiative part of the energy removed from emitter (or decreased emitter
lifetime). However, the scattering (and extinction) cross sections correspond
only to the dipoles inside the scatterer and do not include (all) interference
with the emitting dipole.
In other words, the cross sections calculated by ADDA correspond to the energy
flow through the scatterer surface, which is now not equal to that through the
very large sphere (due to the singularity between these two surfaces). But it
is the latter which correspond to the full power emitted by the system. I
foresee two ways to compute it:
1) through the electric field due to the scatterer on the emitting dipole. This
should be quite easy to implement into ADDA, but will require separate formulae
for different types of emitters (different multipoles, finite size, etc.).
2) by calculating the energy flow in the far-field. This can be done for any
incident field, but requires it to be known not only on the scatterer surface,
but also in the far-field. Alternatively, a multipole expansion of the incident
field will be sufficient. For very small particles and dipole emitter
considering only the total dipole moment of the system (emitter + nanoparticle)
should be a fine approximation.
Finally, the extinction cross section should be calculated by the formulae for
non-plane beams, which is not guaranteed if a field is generated by a code hack
inside GenerateB.c - see AddingBeam for details.Original comment by yurkin on 5 Nov 2012 at 5:17
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Original issue reported on code.google.com by
yurkinon 6 Jun 2012 at 5:01