Designed scattering by composite nanostructures
How to design a nanostructure to scatter light in the direction you want
T.P.S. Kotte (TU Delft - ImPhys/Adam group)
H.P. Urbach – Promotor (TU Delft - ImPhys/Urbach group)
A.J.L. Adam – Copromotor (TU Delft - ImPhys/Adam group)
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Abstract
This thesis investigates how light can be manipulated through directional scattering by nanostructures, as an alternative to traditional methods such as lenses, mirrors, and diffraction gratings. Thanks to modern nanofabrication techniques, light scattering can be controlled by carefully designed nanostructures. In this work, a design method was developed for nanoparticles that scatter light preferentially in a specific direction by combining absorbing and non-absorbing materials, introducing a phase difference in the scattered field. Experimental results with silica–gold particles confirm the theoretical predictions. The theory was subsequently applied to transmission diffraction gratings, in which glass structures combined with metals or semiconductors were fabricated using techniques such as electron-beam lithography. Although metallic gratings exhibited reduced efficiency due to absorption, gratings made with titanium nitride showed the expected performance improvements.