How do you make a light source that is directional, has a controlled wavefront, and a controlled polarization out of an intrinsically incoherent and disordered set of emitters, like fluorophores in an LED phosphor? This is a defining question in the field of light-emitting metasurfaces, with applications in LEDs, incandescent lighting and VR/AR display pixels. While it is understood how to shape intensity, e.g. making LEDs directional with nanostructures, a completely open question is how to shape polarization of emission at will. This touches on an emerging field in nanophotonics: chirality, which in the light field expresses as circular polarization. Circularly polarized fluorescent light sources are for instance pursued for pixels in 3D display technology. You will work on realizing chiral light emitting devices combining both intrinsically chiral emitters, and nanophotonic engineering through optical metasurfaces.
Metasurfaces, i.e., nanostructured 2D scattering surfaces can impact chirality in two ways. On one hand, there is interest in using the geometry of metasurfaces to ‘spoof’ chirality: imparting chiral emission and absorption properties on light-emitting matter that is not itself microscopically chiral, On the other hand, matter such as light emitting molecules may itself be chiral. While molecular chirality is intrinsically weak, there are claims that on the nanoscale optical resonances can be ‘superchiral’, and will boost the enantioselective properties of molecularly chiral absorber and emitter materials.
In this project you will work with novel world-record strength chiral emitter systems derived from OLED (organic light emitting polymer LED) materials developed by M. Fuchter and J. Wade (Oxford Univ. and Imperial College). We aim to address two main questions. First, we aim to uncover the microscopic origin of the record-strength chiral nature of fluorescence from these materials. It is well known in nanophotonics that you can unravel the properties of fluorescent transitions by placing matter in controlled environments (cavities, multilayers), that exert known cavity QED effects. You will extend this toolbox to chiral/polarimetrically resolved versions to elucidate the transition dipole moments, radiative lifetimes and handed far field angular emission properties. Second, we aim to address the question how you can manipulate and enhance microscopic chirality by metasurface resonances.
This project will involve fluorescence microscopy, polarimetry, fluorescence lifetime measurements, transient absorption spectroscopy, metasurface design and nanofabrication, and will build on already available strengths in these techniques as well as numerical and analytical theoretical descriptions. The work is under joint supervision of F. Koenderink at AMOLF and S. Mann at UvA, and benefits for collaboration on the materials aspects with M. Fuchter and J. Wade.
Interested? Please visit the official vacancy web page:
https://amolf.nl/jobs/phd-position-chiral-light-emitting-metasurfaces-1267893
Have more questions? Reach out to s.mann@uva.nl!