On-chip optical communications are in increasingly demand for low-loss, small-footprint and power-efficient waveguiding solutions in the telecom band. However, most integrated optical circuits suffer from high propagation loss and low integration degree. Through manipulating the valley-dependent topological phase of light, we have experimentally demonstrated both robust optical transport and electrical modulation of lightwaves at telecom wavelengths in the valley photonic crystals. With the adoption of valley kink states, the 25 Gbit/s optical signal at 1550 nm is successfully transmitted through a highly twisted interface. Furthermore, an extreme high data rate of 100 Gbit/s is demonstrated with such topological waveguide by wavelength division multiplexing. The electrical tunability of the topological modulators based on thermo-optic effect is also verified, opening a novel route towards active valley kink photonic devices. Our study shows a great possibility of making use of the topological protection in building up high-speed datalinks on a chip.

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The realization of pseudomagnetic fields for lightwaves has attained great attention in the field of nanophotonics. Like real magnetic fields, Landau quantization could be induced by pseudomagnetic fields in the strain-engineered graphene. We demonstrated that pseudomagnetic fields can also be introduced to photonic crystals by exerting a linear parabolic deformation onto the honeycomb lattices, giving rise to degenerate energy states and flat plateaus in the photonic band structures. We successfully inspire the photonic snake modes corresponding to the helical state in the synthetic magnetic heterostructure by adopting a microdisk for the unidirectional coupling. By integrating heat electrodes, we can further electrically manipulate the photonic density of states for the uniaxially strained photonic crystal. This offers an unprecedented opportunity to obtain on-chip robust optical transports under the electrical tunable pseudomagnetic fields, opening the possibility to design Si-based functional topological photonic devices.

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