Optical applications of multilayered nanostructures

New hybrid multilayered nanostructures composed of plasmonic and iron oxide nanoparticles, bound together by organic molecules, were fabricated. These unique structures exhibit interesting and new optical phenomena and can be used to unravel fundamental interactions between light and matter at the nanoscale. In this dissertation we explored new optical effects that were due to plasmon coupling effects and the presence of strong higher order contributions to the optical response of these materials. After the first chapter, which serves as an introductory chapter where the reader is familiarized with the relevant concepts of nanochemistry, we discuss the fabrication of the nanostructures by two different methods, the layer-by-layer method and the new ultrasonic spray coating (USSC) technique. Next we used these structures to investigate new and unusual optical effects, i.e. nonreciprocal asymmetric optical transmission, helical dichroism and nonreciprocal natural optical rotation. Nonreciprocal asymmetric transmission, the dependence of the transmission on the propagation direction, was experimentally demonstrated and a phenomenological model was presented. This model indicates that induced electric quadrupole moments are at the origin of the asymmetric transmission and the nonreciprocal nature of the effect. In a next step we investigated the interaction of chiral multilayered nanostructures with twisted or Laguerre-Gaussian (LG) light. LG light carries orbital angular momentum (OAM) and we showed for the first time that chiral matter can engage with the orbital angular momentum of light in addition to its spin angular momentum. Furthermore, we demonstrated that chiral nanostructures interact differently with light of opposite OAM, an effect that we called helical dichroism. Theoretical results reveal that helical dichroism is based on fundamentally different chiral electric quadrupole contributions compared to circular dichroism, which is dependent on magnetic dipole contributions. Lastly we investigated natural optical rotation in chiral multilayered structures. In addition to an extremely strong reciprocal natural optical rotation we found evidence of a significant nonreciprocal optical rotation component. This effect occurs in the absence of a magnetic field and a phenomenological model was used to elucidate the origin of this effect.

Publication year:2019

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