non-reciprocal lasing in topological cavities of arbitrary geometries
Name: Babak Bahari
Grad Year: 2018
Topological insulator is a material in which helical conducting states exist on the surface of the bulk insulator. These states can transport electrons or photons at the boundary without any back scattering, even in presence of obstacles enabling to make topological cavities with arbitrary geometries that light can propagate only in one direction. In this contribution, we theoretically and experimentally demonstrated the first non-reciprocal topological laser that operates at telecommunication wavelengths. The unidirectional stimulated emission from edge states is coupled to a selected waveguide output port with an isolation ratio of 11 dB. Topological cavities are made of hybrid photonic crystals (i.e., two different photonic crystals) with distinct topological phase invariants, which are bonded on a magnetic material of yttrium iron garnet to break the time-reversal symmetry. The possibility to construct geometry-independent cavities opens a new paradigm in cavity quantum electrodynamics and photonic integration, as it enables denser packing of components and sources of arbitrary form-factors. This prospect will alleviate the, otherwise stringent, constraints to use preset cavities that leave much chip space unused. Topology also naturally addresses the pressing need for non-reciprocal components that protect sources against back scattering. Our experimental demonstration, paves the way to develop complex non-reciprocal topological devices of arbitrary geometries for integrated and robust generation and transport of light in classical and quantum regimes in which information can robustly flow between sectors characterized by different topological indices.
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