Wavefront shaping techniques allow one to focus light inside and through turbid media. In order to gain a better understanding how light evolves inside a scattering random medium while shaping the incident wavefront, it is beneficial to know the electromagnetic field within the entire medium, which is difficult to achieve in experiments. Here we investigate wavefront shaping techniques with numerical simulations based on Maxwell's equations to examine various effects of wave propagation in randomly scattering media. First, we calculate numerically monochromatic plane wave solutions for a given scattering medium for different incident k-vectors. With these plane wave solutions we are able to simulate complex-shaped incident wavefronts impinging on the scattering medium. This enables us to scan and tilt the incident complex wavefront after solving Maxwell's equations and to examine the electromagnetic field inside the medium. Due to the fact that we have access to the electromagnetic field of the plane wave illumination from different angles, it is easy to phase-optimize an incident wavefront by conjugating the known phase at a certain location. Because of the separate calculation of the plane wave solutions and the possibility to simulate different incident wavefronts by superimposing these plane wave solutions, our method is very dynamic and versatile. In summary, our simulation approach contributes to the understanding of light propagation in strongly scattering media such as biological tissue and to the improvement of medical imaging techniques.
Christoforos Moutafis, Felix Büttner, Andre Bisig, Benjamin Krüger, C. A. Vaz, Michael Foerster, Mohamad-Assaad Mawass, Michael Schneider, Christian Gunther, Jan Geilhufe, C. von Korff Schmising, J. Mohanty, B. Pfau, Stefan Schaffert, Tomek Schulz, Markus Weigand, Henk Swagten, Jörg Raabe, Mathias Kläui, Stefan Eisebitt
Skyrmions are topologically protected particle-like configurations, with a topological
complexity described by their Skyrmion number. In magnetic systems, they have been
numerically predicted to exhibit rich dynamics, such as the gyrotropic and breathing
modes, dominated by their topology. Recent experimental advances brought their static
manipulation well under control. However, their dynamical behaviour is largely
unexplored experimentally. In this work, we provide with the first direct observation of
eigenmode skyrmion dynamics. In particular, we present dynamical imaging data with
high temporal and spatial resolution to demonstrate the GHz gyrotropic mode of a
single skyrmion bubble, as well as the breathing-like behaviour of a pair of skyrmionic
configurations. We use the observed dynamical behaviour to confirm the skyrmion
topology and show the existence of an unexpectedly large inertia that is key for
accurately describing skyrmion dynamics. Our results demonstrate new ways for
experimentally observing skyrmion dynamics and provide a framework for describing
their behaviour. Furthermore, the results outline a link between the dynamical behaviour
of skyrmions and their distinct topological properties, with possible ramifications for
skyrmionic spin structures research including technological applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.