Departmental Seminar

Anomalous Floquet phases and topological transitions in photonic lattices

Dr Daniel Leykam
Nanyang Technological University, Singapore
Wednesday 4 May 2016 11am–12pm

Floquet models governed by periodically driven Hamiltonians can reveal topological phenomena inaccessible in static systems. For example, the two dimensional "anomalous Floquet insulator" phase exhibits protected unidirectional edge modes despite all Bloch wave bands having zero Chern number. At optical frequencies periodic driving has been emulated by light propagation in helical photonic lattices, but the anomalous Floquet phase could not be observed due to the lack of tunable phase transitions and high bending losses of the original designs. In this talk I will show that these limitations can be overcome using a class of staggered helical photonic lattices and present a novel numerical method to compute their band structure. At transitions between trivial and nontrivial phases the Floquet band structure hosts a single unpaired Dirac cone, enabling the observation of effects such as weak antilocalization. The low losses and tunable topological transitions of this design raise the prospect of nonlinear or actively-controllable topological wave-guiding devices.

Contact

Dr Daniel Leykam
daniel.leykam@gmail.com

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