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Terahertz waveguide: the fundamental component for sustainable world connectivity

Recent advances in the field of photonics and topological physics can be combined to offer a solution to planar 6G, above 100 GHz, communication devices. As specific examples, we demonstrate that a hybrid photonic crystal waveguide can support a single-mode transmission covering 0.367–0.411 THz (over twice as wide as that of all-silicon photonic crystal waveguides). By breaking the photonic crystal symmetry, topologically protected modes can be introduced with a single mode linear-dispersion transmission window (over 0.143–0.162 THz) and robust transmission around sharp corners without any deterioration in the bandwidth. Such topologically protected waveguides, here produced using simple 3D printing techniques, offer a unique simplification in design. The absence of coupling to back-propagating modes removes the requirement to carefully design away spurious resonances, offering a pathway to a truly versatile planar platform for integrated 6G devices with low loss and wide bandwidth.