# SPP 1839 „Tailored Disorder“

**Source**: https://www.cs.tum.de/spp1839/
**Parent**: https://www.cs.tum.de/en/research/focus/biogenic-materials

The priority programme “Tailored Disorder - A
science- and engineering-based approach to materials design for advanced
photonic applications” (SPP 1839) is an effort to develop this novel
field of research and foster new technologies to fabricate large scale
materials with defined photonic properties based on deliberately and
controlled disorder. Therefore, the SPP 1839 relies on the interplay of
five research areas:

- **Biology**: Investigations of the
  composition and organization of biologically evolved photonic
  structures and their resulting photonic properties.

- **Physics**: Photon diffusion and scattering in disordered media and their collective effects.

- **Theory and Computer Science**: Modeling and simulation of disorder-based artificial or bio-genic photonic structures.

- **Material Science**: Fabrication of artificial or bio-mimetic structures that utilize disorder to define their functionality.

- **Chemistry**: Chemical functionalization or syntheses that facilitate control over the formation of disorder.

Three major effects can emerge in disordered
media: (i) isotropic scattering, which is potentially useful for light
sources without directed emission, (ii) highly directional scattering,
which despite disorder minimizes demand towards material spatial
accuracy (cost-effective) and (iii) localization, which slows down
light or can even trap photons inside the disordered structure. This
leads to cavity-like behavior useful for tailored interaction with
secondary material effects, e.g. gain for lasing. All these effects can
in addition be highly wavelength dependent and can be controlled by
the many degrees of freedom inside a tailored disorder photonic
material, promising a nearly unlimited freedom to tailor photonic
responses.

The SPP 1839 is established by the Deutsche
Forschungsgemeinschaft (DFG, German Research Foundation) since 2014. The
program is designed for running up to six years.

## Official programme description

The SPP “Tailored disorder – A science- and
engineering-based approach to materials design for advanced photonic
applications” investigates photonic properties of material composites
with deliberately introduced irregularities in their geometry and
composition. From fundamental scientific questions to various subfields
of material science required for technological implementation of
optimized materials all aspects will be explored. By combining
inspiration from biological systems, results from physics, chemical
approaches and validation from simulation, together with material
science and engineering the SPP will enable the design of novel advanced
photonic materials. This will finally lead to custom-made devices for
a variety of photonic applications, their performance related to
tailored disorder within 3D micro- and nano-architectures.

Recent research shows strict periodicity in photonic
devices not being the only possible way to implement a desired
functionality and a defined degree of disorder can give rise to
unforeseen optical effects. Tailored disorder in materials can therefore
propose design guidance to produce resilient materials, fulfilling
the requirements for multi-functionality in complex environments and
application fields. However, there is a large gap between theoretical
considerations and practically available materials and devices. Up to
now, fabrication routes to tailor disorder in a material have been
scarce. The objectives of the SPP comprise the successful production of
materials containing a defined degree and type of disorder with
predictable photonic properties resulting in technological
demonstrators. The theoretical and artificial systems that have been
identified so far are not only limited with respect to property and
performance control, but are also too expensive for any widespread
technological implementation. Thus, new fabrication approaches and
synthetic routes are required to merge scientific innovation and
understanding with advanced engineering strategies.

One of the major goals is the identification of
nano-architectures in biological systems, which produce a specialized
optical response by means of disordered photonic structures e.g. in
butterflies and beetles. The selective refraction and diffraction of
light will subsequently be studied experimentally and theoretically with
emphasis on (dis)order and (ir)regularity, identifying possible
blueprints for artificial, bio-inspired nano-architectures. Finally the
most promising approaches will be experimentally replicated via
lab-based nano-fabrication.

To advance this field beyond pure observation, a
truly interdisciplinary approach is taken relying on (i) biological
blueprints followed by (ii) bio-inspired replication and (iii)
ultimately identification of design rules for artificial
synthesis/-patterning and optimization of photonic nano-architectures
with tailored disorder.

\