Dresden 2017 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 85: Topological Insulators III (joined session with TT)
HL 85.1: Talk
Friday, March 24, 2017, 09:30–09:45, POT 251
Time-dependent defects in photonic topological insulators — •Christina Jörg1, Fabian Letscher1,2, Michael Fleischhauer1, and Georg von Freymann1,3 — 1Physics Department and Research Center OPTIMAS, University of Kaiserslautern, Germany — 2Graduate School Materials Science in Mainz, Kaiserslautern, Germany — 3Fraunhofer-Institute for Physical Measurement Techniques (IPM), Kaiserslautern, Germany
To model topological insulators by means of classical optics, we fabricate arrays of evanescently coupled waveguides. These waveguides are about 1 µm in diameter at an aspect ratio of 1:500, and helically curved. The inverse of the waveguide array is fabricated via direct laser writing in a negative-tone photoresist. Subsequently the sample is infiltrated with a material of higher refractive index, creating low-loss 3D waveguides. Arranging the waveguides on a honeycomb-lattice, a robust edge mode exists due to topological protection [1]. This means that light moves along the edge unidirectionally, and even walks around defects without backscattering. Here, we discuss defects with time-dependent coupling, i.e., one waveguide with a different helicity than the rest of the waveguides. We examine three kinds of time-dependent defects: a) a straight waveguide, b) a waveguide with opposite helicity, c) a waveguide with same helicity but shifted by half a helix pitch in the z-direction. In all three cases the edge mode moves along the edge regardless of the defect, going partially around the defect and partially through it.
[1] M. C. Rechtsman et al., Nature 496, 196-200 (2013).