Our Motivation

The S3 research group supports the vision of PhoenixD - the development of the digital optics of the future - in particular through its research into miniaturisation. Understanding the reaction of a material at an atomic level is important for the targeted influencing of light. This interaction is to be modified and optimised in order to drastically reduce the size of optical components and systems.

Glass as a traditional material for optical components is not suitable for miniaturised precision optics. Silicon, for example, is much more suitable. Using processes that are very well known and available from microelectronics, optical systems with complex functionality and maximum precision can be manufactured on a nano and micrometre scale. Another major advantage is the simple electrical connection and co-integration of microelectronic assemblies.

In thin diamond waveguides, interactions that occur in glass fibres over a length of several kilometres can be observed after just a few millimetres. Metamaterials offer a further approach to miniaturisation. Complex optical structures and material composites enable customised optical functionalities that go far beyond naturally available properties.

Another focus of the working group is the manipulation of the optical properties of a material using light. Such all-optical approaches appear promising for ultra-fast, precise and compact optical systems.

Our research

Research in the S3 working group focuses on light-matter interaction on all length scales from the atomic to the macroscopic level. Various physical variables such as pressure, temperature, current or magnetic field play a role here. The specialist areas concerned are, in particular, ultrashort pulse optics, non-linear optics and nanophotonics (Figure 1).

Efficient computing methods are being developed for the generation, conduction and manipulation of light in miniaturised optical systems. These enable the design and simulation of systems on all scales. The working group also conducts research into the simulation of laser-based manufacturing processes.

The simulation shows how the mutual attraction of two optical solitons leads to the formation of a soliton molecule.

Material simulation is of particular importance. Materials such as silicon or diamond are optically highly non-linear. This is a great advantage for the integration of optical components with light-light interaction, but at the same time places very high demands on the optical simulation. The complexity is further increased by the fact that in semiconductors such as silicon, the interaction of light with free charge carriers must also be taken into account in addition to the non-linearity.

Metamaterials promise the construction of practically arbitrary spatial distributions of the refractive index and other optical quantities that are unthinkable in natural materials. In this way, light can be freely manipulated to a high degree. The simulation of such small-scale systems requires very specific approaches such as so-called "transformation optics".

Machine learning techniques play an important role in researching the properties and improving the design of advanced materials. The working group uses machine learning in particular to determine interatomic potentials. The aim is to develop an ab-initio multiscale model that combines quantum mechanical density functional theory with classical molecular dynamics and finite element methods (Figure 2).

Interatomic potentials obtained by machine learning from molecular dynamics simulations lead to an efficient ab-initio multiscale model for the description of optical materials.

Material surfaces and interfaces are particularly suitable for manipulating light. Special combined light-current oscillation states (surface plasmon polaritons) can be excited at the interface between a metal and a dielectric. In these states, light is concentrated in areas that are far smaller than the optical wavelength.

Dielectric or metallic nanoparticles can be used to excite surface plasmons in a localised manner. This can increase the sensitivity of certain optical sensors many times over. Meta-surfaces with artificial nanostructures are now also being produced that can select and influence specific optical oscillation modes (Figure 3).

Invisible particle: A nanostructured metasurface causes incident light to practically "flow around" a particle on the surface.

The interaction and superposition of electrical and magnetic resonances in dielectric particles and nanostructured surfaces open up completely new ways of efficiently controlling light in dimensions below the wavelength. To this end, the working group develops and simulates concepts for ultra-thin lenses, filters, polarisers, sensors and other components.

In addition to directly influencing light via the static properties of optical materials, light can also be manipulated indirectly, for example by means of pressure or temperature. The description of the interplay of thermo-mechanical and optical properties using a multi-physics simulation allows, for example, the modelling of piezoelectric or flexoelectric materials, but also the controlled manipulation of light propagation in the material in question.

The S3 working group co-operates with the S2 working group in the simulation of optical materials and with the M1 working group in the development of new optical materials. Co-operation with the M2 working group is also important, particularly with regard to laser material processing. In collaboration with S1, optical functionalities and components are combined to form optical systems and S4 provides support with theoretical analyses and multidimensional simulations.