# 13 - Control of scattering interaction in disordered two-dimensional arrangements of silicon nanoparticles

**Source**: https://www.cs.tum.de/spp1839/projects/1st-period-2015-2018/13.html
**Parent**: https://www.cs.tum.de/spp1839/projects.html

We aspire to obtain complete control of the
complex reflection and transmittance properties of optical nanosurfaces
- two-dimensional arrangements of scattering nanoparticles - with
near-zero absorption loss and subwavelength lateral resolution.A
cornerstone of this research is a strong interaction of light with
matter, which is commonly observed for a periodic modulation of the
nanosurface permittivity, e.g., by periodic arrangements of scattering
nanoparticles across a surface. The coherent built-up of many scattering
events allows controlling the optical response and entails the
observation of high quality optical resonances. However, the necessary
long-range interaction is often detrimental for harvesting such
resonances in applications. The optical response is sensitive to the
external illumination and cannot be controlled across an extended
spectrum. Introducing disorder into such structures can overcome these
problems, but the resulting nanosurfaces usually suffer from notable
loss of response strength. Moreover, controlling the optical response
with high spatial resolution is not possible.To bypass this obstacle,
the required strong light-matter interaction can also be achieved with
scattering nanoparticles that exhibit an individual resonant response to
an external field. This type of response is for example supported by
nanoparticles made from high permittivity dielectrics, e.g.
semiconductors at frequencies below the band edge. Compared to plasmonic
nanoparticles they are appealing since they do not suffer from
absorption, leaving scattering as the only remaining source of
loss.However, controlling the optical response of arrangements of such
high-permittivity nanoparticles at small length scales poses a
challenge, as the mutual radiative interaction among all nanoparticles
causes the optical response to explicitly depend on the arrangement of
other nanoparticles at distances far apart. Here, we suggest adjusting
the distance across which long-range interaction is observed by
introduction of a tailored disorder to the arrangement of the scattering
nanoparticles.

Moreover, tailored disorder not just in the position
but also in the geometry of individual nanoscatterers allows to
control both the far- and the near-field interaction. Applying these
concepts to nanosurfaces composed of scattering nanoparticles with an
individually tailored scattering response, e.g. where the electric and
magnetic dipolar contribution are of same (complex) amplitude, will
provide us with full control of the wave front of the reflected and
transmitted light from such disordered nanosurfaces. Combined with the
high efficiency of the individual nanoscatterer, we have access to a
plethora of highly efficient, flat and lightweight optical devices
including planar lenses, beam-shapers, beam deflectors, and holograms.
To reach this project goal, we have combined theoretical and
experimental expertise, both for the fabrication and the
characterization.

## Contributors:

- [Prof. Thomas Pertsch](http://www.iap.uni-jena.de/nanooptics.html)
- [Prof. Carsten Rockstuhl](https://www.tfp.kit.edu/rockstuhl.php)
- [Dr. Isabelle Staude](http://www.acp.uni-jena.de/staude.html "Opens internal link in current window")
- Aso Rahimzadegan

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