Publications

Phase elements can improve the performance and reduce the size of imaging systems, thanks to the additional degrees of freedom that are offered by the independent phase gradient on top of a refractive/reflective surface. Possible implementations include diffractive elements or metasurfaces, but these suffer from diffractive dispersion. Similar optical functionality however can be provided by thin, curved Fresnel optics, which solely rely on ...

In this abstract we report on our work towards integrating photovoltaic (PV) solar cells into a Concentrated Solar Power (CSP) configuration. First we introduce the motivation for such a concept and the targeted demonstration, utilizing more efficiently the available solar energy, through spectrum splitting (and capturing also diffuse light as a side effect). Then we discuss the implementation and evaluation in 1- cell laminates, followed by ...

This PhD thesis presents research conducted within the framework of the SBO project "Quantum Dots for On-Chip Luminescent Downconversion (QDoCCO)". The project's main goals were the development of novel InP quantum dots, the investigation of innovative encapsulation methods for these nano-particles,
and the creation of spectrum-by-design LED demonstrators using InP quantum dots. This final goal, the realization of spectrum-by-design ...

In illumination optics, the goal is to modify a light source’s spatial distribution to achieve a specific irradiance target. By using freeform surfaces, the emitted light can be transformed into arbitrary irradiance patterns. Despite significant advances in freeform optics design, mostly for ideal light sources, current methods offer limited control over the surface shape, generally resulting in globally convex or concave surfaces. In an ...

The external quantum efficiency of light-emitting diodes (LEDs) emitting in the spectral range from 510 to 600 nm is much smaller than blue- or red-emitting LEDs. The current strategy to overcome this so-called green gap is the color conversion of the emitted light by an efficient violet or blue III-nitride-based LED. Colloidal quantum dots (QDs) are promising candidates thanks to their narrow, size-tunable emission spectrum. Single-color ...

The bidirectional scattering-surface reflectance distribution function (BSSRDF) describes the radiance originated by the volume scattering and the surface reflectance of any position on the surface of a sample, when it is directionally irradiated at any other position. The present state of the technology for appearance rendering requires a more detailed physical description of translucent objects by traceable measurements of the BSSRDF. This ...