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Significance Liquid crystals are complex fluids that combine a unique ability to manipulate light with the reconfigurability of soft materials. They are at the core of modern display technology. Here, we suggest that nematic liquid crystals can also be used as building blocks of topological materials key to realize protected unidirectional waveguides, sensors, and lasers. Building on recent advances in liquid-crystal technology, we propose that suitable spatial modulations of the nematic director field are sufficient to assemble topological photonic materials. These ideas pave the way for fully reconfigurable photonic devices based on topologically protected states.
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Tunable unidirectional surface plasmon polaritons at the interface between gyrotropic and isotropic conductors
Unidirectionally propagated electromagnetic waves are rare in nature but heavily sought after due to their potential applications in backscatter-free optical information processing setups. It was theoretically shown that the distinct bulk optical band topologies of a gyrotropic metal and an isotropic metal can enable topologically protected unidirectional surface plasmon polaritons (SPPs) at their interface. Here, we experimentally identify such interfacial modes at terahertz frequencies. Launching the interfacial SPPs via a tailored grating coupler, the far-field spectroscopy data obtained reveals strongly nonreciprocal SPP dispersions that are highly consistent with the theoretical predictions. The directionality of the interfacial SPPs studied here is flexibly tunable by either varying the external field or adjusting the metallic characteristics of the bulk materials. The experimental realization of actively tunable unidirectional SPPs sets the foundation for developing nanophotonic information processing devices based on topologically protected interfacial waves.
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- Award ID(s):
- 1741673
- PAR ID:
- 10252172
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optica
- Volume:
- 8
- Issue:
- 7
- ISSN:
- 2334-2536
- Format(s):
- Medium: X Size: Article No. 952
- Size(s):
- Article No. 952
- Sponsoring Org:
- National Science Foundation
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