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Non-reciprocal and Chiral Plasmonics

Faraday rotation

Non-reciprocity

We introduce non-reciprocity into plasmonic systems to enhance the magneto-optical effects in thin films, in particular, the Faraday effect. The Faraday Effect describes the phenomenon where light traveling through a magnetized material experiences a rotation of its polarization plane. But different from optical activity, the Faraday Effect is not reciprocal. In nature, it occurs in materials such as quartz and various rare earth garnet crystals. In these materials the Faraday rotation per unit length is typically small as well as the other magneto-optical phenomena. As a result, nonreciprocal devices based on magneto-optical effects in these materials are quite bulky. We hybridize magneto-optical materials with plasmonic structures, explore different approaches to enhance the magneto-optical effects in small material volumes, analyse the physics behind such enhancement and demonstrate the concepts by naofabrication and optical characterizations in experiment. Our research goal is to develop compact and integrated optical systems to enhance Faraday rotation and other magneto-optical effects that are of technological relevance.

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Chiral plasmonic oligomer

Chirality

Objects that cannot be superposed onto their mirror image are called chiral. The most prominent example is the human hand, but also many molecules that are of importance for chemistry, biology or medicine are chiral. However, interactions with the achiral world are independent of their handedness. One relies on other chiral objects to detect the handedness of such chiral molecules. A common aproach uses the differential absorption of circularly polarized light, but this effect is rather weak.

Our research interests are twofold: First, we study chiral plasmonic nanostructures whose chiral optical response is much bigger than for any chiral molecule occuring in nature. We develop techniques to fabricate these highly asymmetric structures and analyze the origin of the chiral response for different designs. The second topic is the incorporation of natural chiral materials in plasmonic systems. Our goal is to enhance the chiral optical response of these molecules and detect their handedness with a sensitivity that is several orders of magnitude higher than for current enantiomer sensors.

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