Waveguide superlattices with artificial gauge field toward colorless and low-crosstalk ultrahigh-density photonic integration

Dense waveguides are the basic building blocks for photonic integrated circuits (PICs). Due to the rapidly increasing scale of PIC chips, high-density integration of waveguide arrays working with low crosstalk over broadband wavelength range is highly desired. However, the subwavelength regime of such structures has not been adequately explored in practice. We propose a waveguide superlattice design leveraging the artificial gauge field mechanism, corresponding to the quantum analog of field-induced n-"photon"resonances in semiconductor superlattices. This approach experimentally achieves -24 dB crosstalk suppression with an ultrabroad transmission bandwidth more than 500 nm for dual polarizations on the Si₃N₄ platform. The fabricated waveguide superlattices support high-speed signal transmission of 112 Gbit/s with high-fidelity signal-to-noise ratio profiles and bit error rates. This design, featuring a silica upper cladding, is compatible with standard metal back-end-of-the-line processes. Based on such a fundamental structure, which is readily transferable to other platforms, passive and active devices over versatile platforms can be realized with a significantly shrunk on-chip footprint, thus it holds great promise for significant reduction of the power consumption and cost in PICs.