Optical metasurfaces for lighting applications

The development of light emitting diode technology in the past few decades has revolutionized the lighting industry. Light emitting diodes have longer life times, smaller footprints and lower power consumption than traditional light sources, so today they have taken over most of the lighting market. With the development of the light emitting diode technology comes a need to develop efficient secondary optics to shape the light from the diodes. In many applications these secondary optics are bulky, and thus reduce the advantage of the small footprint of the diodes. A popular way of shaping light from light emitting diodes for custom applications is with freeform lenses. These lenses can be designed for almost any application, but become increasingly difficult to manufacture as the complexity of the lenses increase.
In this thesis we investigate an alternative approach to designing optics for light emitting diodes that do not compromise the footprint of the diodes and for which the fabrication difficulty is constant. This can be done with metasurfaces. We use the principles of optimal transport from non-imaging optics to develop a design framework for calculating the phase profile of a non-imaging metasurface. Our approach is based on the Monge-Ampere approach known from freeform optics and the generalized law of refraction which is extensively used in meta optics. We implement a one dimensional version of our framework numerically, and show how this simple version can be used to calculate two dimensional phase profiles in cases with cylindrical symmetry.
We delve into how we can implement the calculated phase profiles in physical samples. This includes choosing a material platform, considering how to dicretize the phase profile and the calculation of look up tables for meta atoms. We use these considerations to create real designs, and develop a cleanroom fabrication process flow for fabricating the samples. Finally we build an optical setup for characterization of the samples and the light source used to illuminate them. We demonstrate the complete process from design to characterization with a sample, and we find that our optical measurements are in good agreement with our simulations. The work we present here is a good step in the direction of establishing a solid platform for designing optical metasurfaces for lighting applications.