## Aspects of photonic topological insulators

**Speaker:**Prof. Mikael Rechtsman, Penn State

**When:**December 4, 2015 (Fri), 12:00PM to 01:00PM (add to my calendar)

**Location:**SCI 352

*This event is part of the Biophysics/Condensed Matter Seminar Series. *

Abstract: I will present the observation of the topological protection of light - specifically, a photonic Floquet topological insulator. Topological insulators (TIs) are solid-state materials that are insulators in the bulk, but conduct electricity along their surfaces - and are intrinsically robust to disorder. In particular, when a surface electron in a TI encounters a defect, it simply goes around it without scattering, always exhibiting – quite strikingly – perfect transmission. The structure is an array of coupled helical waveguides (the helicity generates a fictitious circularly-polarized electric field that leads to the TI behavior), and light propagating through it is ‘topologically protected’ from scattering. Topological protection therefore has the potential to endow photonic devices (e.g., delay lines, isolators, directional couplers, resonators) with quantum Hall-like robustness. Time permitting, I will also discuss photonic topological quasicrystals and experimental results on non-Hermitian topological transition.