Quantum Optics Seminar by Nir Rotenberg – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Nir Rotenberg

Light fields above nanophotonic objects, such as photonic crystal waveguides, can be extremely rich in structure. We have, recently, explored these light fields, searching for features such as optical singularities.  At the nanoscale, light fields in the neighborhood of such singularities can interact with nanoscopic structures in interesting ways, for example by causing them to spin, or rotate about the singularity.  In this talk, I will present the results of our search for structure in light fields, beginning with the tool that we use – a near-field scanning optical microscope – and how we can use it to detect both electric and
magnetic near fields.  In these electromagnetic near fields of a photonic crystal waveguide we identify phase and polarization singularities.  I will show that these singularities follow different trajectories in the three-dimensional space above the crystal surface, and behave in ways that cannot be reproduced by far-field optics. 
I also present near-field measurements that exploit the local properties of the optical modes of a photonic crystal waveguide to control emission from a nanoscopic emitter.  Specifically, both experiments and theoretically modeling show that near unity coupling of emission direction to dipole helicity (associated with a spin-changing transitions) is possible in a photonic crystal waveguide.