Configurable topological beam splitting via antichiral gyromagnetic photonic crystal

Configurable topological beam splitting via antichiral gyromagnetic photonic crystal
Fig. 1. Construction of antichiral gyromagnetic photonic crystal. (a) Schematic illustration of antichiral gyromagnetic photonic crystal. (b) The first Brillouin zone of honeycomb lattice. (c) Nonmagnetized gyromagnetic photonic crystal. (d) Uniformly magnetized gyromagnetic photonic crystal. (e) Compound magnetized gyromagnetic photonic crystal. Credit: Opto-Electronic Science (2022). DOI: 10.29026/oes.2022.220001

Topological insulators, whose bulky states are prohibited while surface/edge states are conductive and topologically protected. Recent advances in topologically protected edge states have drawn growing attention in the optics and photonics community. In 2008, Raghu and Haldane first theoretically predicted that a topologically protected chiral one-way edge state can be created by analogy to the integer quantum Hall effect in a two-dimensional electron gas system, where the one-way edge states propagate along the opposite directions at two parallel edges of a gyromagnetic photonic crystal [Phys. Rev. Lett. 100, 013904 (2008)].

In 2020, the research group of Prof. Zhi-Yuan Li from South China University of Technology theoretically proposed another intriguing case where the one-way at two opposite parallel zigzag edges can propagate in the same direction, and they are called antichiral one-way edge states [Phys. Rev. B 101, 214102 (2020)]. To date, antichiral one-way edge states have been studied in various fermionic and bosonic systems; however, many of studies only focused on the demonstration of antichiral one-way transport property, and few of them touch on the unique properties of antichiral topological systems and novel applications.

A new Opto-Electronic Science study reports the and observation of topological beam splitting with an easily adjustable right-to-left ratio in an antichiral gyromagnetic photonic crystal. The splitter is compact and configurable, has high transmission efficiency, allows for multi-channel utilization, is crosstalk-proof, and is robust against defects and obstacles. This performance is attributed to the peculiar property that antichiral one-way edge states exist only at the zigzag edge but not at the armchair edge of antichiral gyromagnetic photonic crystal. When they combine two rectangular antichiral gyromagnetic photonic crystals holding left- and right-propagating antichiral one-way edge states, respectively, bidirectionally radiating one-way edge states at two parallel zigzag edges can be achieved. Finally, the researchers designed a topological beam splitting with the configurable splitting ratio that can easily be adjusted by simply changing the source excitation condition. These can enrich the understanding of fundamental physics and expand topological photonic applications.

Configurable topological beam splitting via antichiral gyromagnetic photonic crystal
Fig. 2. Compound antichiral gyromagnetic photonic crystal supporting bidirectionally radiating one-way edge states. (a) A clear look at the fabricated sample with the upper cladding layers removed. (b-c) Simulation results of without and with metallic obstacles (yellow cylinders) respectively. Unprocessed transmission data measured at four one-way waveguide channels (d-g) without and (h-k) with metallic obstacles. Credit: Opto-Electronic Science (2022). DOI: 10.29026/oes.2022.220001

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More information: Jianfeng Chen et al, Configurable topological beam splitting via antichiral gyromagnetic photonic crystal, Opto-Electronic Science (2022). DOI: 10.29026/oes.2022.220001
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Citation: Configurable topological beam splitting via antichiral gyromagnetic photonic crystal (2022, May 31) retrieved 8 August 2022 from https://phys.org/news/2022-05-configurable-topological-antichiral-gyromagnetic-photonic.html
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