TY - GEN A1 - Poulikakos, Lisa A1 - Gutsche, Philipp A1 - McPeak, Kevin A1 - Burger, Sven A1 - Niegemann, Jens A1 - Hafner, Christian A1 - Norris, David T1 - A Far-Field Interpretation of the Optical Chirality T2 - Frontiers in Nanophotonics (Congressi Stefano Franscini) N2 - A chiral structure is not super-imposable with its mirror image. Most commonly found in organic molecules, chirality can also occur in other systems, such as electromagnetic fields, where circularly polarized light is the most widespread example. Chiral electromagnetic fields can be a useful tool for biosensing applications. In particular, it has been shown that chiral plasmonic nanostructures have the ability to produce strongly enhanced chiral near-fields. Recently, our group has developed chiral plasmonic nanopyramids, which have the ability to focus chiral near-fields at their tip. This could enable chiral sensing at the single-molecule level. Chiral near-fields can be characterized in terms of the “optical chirality density”. This time-even and parity-odd pseudoscalar was first derived by Lipkin and was found to follow a conservation law analogous to the energy conservation of electromagnetic fields. More recently, Tang and Cohen identified the physical meaning of the “optical chirality density” as the degree of asymmetry in the excitation rate of a chiral molecule. However, how this near-field interpretation of the optical chirality could translate into the far-field is not well understood. Here, we formulate a far-field interpretation by investigating the conservation law for optical chirality in matter, and performing time-averaging in analogy to Poynting’s Theorem. In parallel to extinction energy, we define the “global chirality” as the sum of chirality dissipation within a material and the chirality flux leaving the system. With finite-element simulations, we place a dipole source at locations of enhanced local chirality and investigate the global chirality and ellipticity of emitted light in the far-field. Interestingly, we find that lossy materials with a complex dielectric function have the ability to generate global chirality when excited by achiral light. In particular, chiral plasmonic nanostructures are found to act as effective global chirality generators. The global interpretation of optical chirality provides a useful tool for biosensing applications with chiral plasmonic nanostructures, where the detection is routinely performed in the far-field. Y1 - 2015 ER - TY - GEN A1 - Gutsche, Philipp A1 - Poulikakos, Lisa A1 - Burger, Sven A1 - Hammerschmidt, Martin A1 - Schmidt, Frank T1 - Optical chirality: conservation law in arbitrary space T2 - 606. WE-Heraeus-Seminar on Nanophotonics and Complex Spatial Modes of Light N2 - The introduction of the near-field quantity of optical chirality has emerged in various numerical and few experimental studies of local chirality enhancement due to its relation to the excitation rate of chiral molecules. This time-even pseudoscalar has been dismissed as being a higher-order version of helicity. Nevertheless, we revisit the derivation of the underlying conservation law and define optical chirality in media similar to. We identify the mechanism of chirality conversion by either inhomogeneous or anisotropic space to complement the conservation of optical chirality. The conservation law of optical chirality in arbitrary space enables the extension of the concept of polarization to the near-field where no distiniguished propagation direction of light is present. We show that the connection of electromagnetic energy and optical chirality provide the ability to define a circular polarization basis in time-harmonic near-field analysis. In order to illustrate our theory, we present electromagnetic field simulations of simple as well as more complex nanostructures. Results using the well-known far-field polarization concept are readily reproduced and extended from the point of view of chirality conversion. Y1 - 2016 ER - TY - GEN A1 - Wilson, Jon A1 - Herrmann, Sven A1 - Gutsche, Philipp A1 - Burger, Sven A1 - McPeak, Kevin T1 - The Chiral Coefficient: Rapid Optimization of Broadband Plasmonic Chirality T2 - 2016 MRS Fall Meeting & Exhibit Y1 - 2016 ER - TY - GEN A1 - de Lasson, Jakob Rosenkrantz A1 - Frandsen, Lars Hagedorn A1 - Burger, Sven A1 - Gutsche, Philipp A1 - Kim, Oleksiy S. A1 - Breinbjerg, Olav A1 - Sigmund, Ole A1 - Mork, Jesper A1 - Gregersen, Niels T1 - Comparison of four computational methods for computing Q factors and resonance wavelengths in photonic crystal membrane cavities T2 - Proceedings of the 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics Y1 - 2016 UR - http://jakobrdl.dk/presentationfiles/2016/META16Poster_Niels_July2016.pdf ER - TY - GEN A1 - Gutsche, Philipp A1 - Nieto-Vesperinas, Manuel A1 - Mäusle, Raquel A1 - Burger, Sven T1 - Chiral Nanophotonics: Theory and Simulation T2 - Doctoral Summer School on Nanophotonics and Metamaterials, ITMO University N2 - The interaction of light and chiral matter is subject of recent research both in fundamental science and applications. Among these are the helicity of electromagnetic fields described with the optical chirality density and emitters sensitive to circular polarization employed in quantum communications. In the weak coupling regime of chiral emitters, we analyze the conversion of chirality which can be regarded as an analogue to absorption of energy describing the change of circular polarization of the incident field. This enables the tailoring of chiral near-fields close to metamaterials, e.g. composed of gold helices, and gives insights into extinction measurements such as circular dichroism. We show relation of the weak and strong coupling regime. The latter can be modelled with cross electric-magnetic polarizabilities or with effective chiral materials, i.e. bi-anisotropic media. Accordingly, we motivate the necessity for rigorous numerical simulations to accurately describe chiral light-matter interaction. Y1 - 2017 ER - TY - GEN A1 - Gutsche, Philipp A1 - Burger, Sven A1 - Nieto-Vesperinas, Manuel T1 - Fundamentals and Applications of an Optical Theorem for Chiral Optical Fields T2 - 4th International Conference on Optical Angular Momentum N2 - The helicity of light is of great interest in both fundamental research and in applications such as dichroism spectroscopy. Its time-harmonic formulation is directly proportional to the density of optical chirality. Recently, both an helicity optical theorem (HOT) and a chirality conservation law (CCL) have been formulated for arbitrary scatterers taking into account an underlying continuity equation of this quantity. We summarize these two equivalent fundamental laws and analyze their potential applications. Y1 - 2017 ER -