Ultrabroadband Light Coupling for Integrated Photonics via Nonadiabatic Pumping

Abstract Enlarging bandwidth capacity of the integrated photonic systems demands efficient and broadband light coupling among optical elements, which is a vital issue in integrated photonics. Here, an ultrabroadband light coupling strategy based on nonadiabatic pumping is developed, and the designs in thin‐film lithium niobate on insulator platform are experimentally demonstrated. It is found that nonadiabatic transition produces a decreased dispersion of the phases related to eigenstates in the waveguides. As a consequence, high‐efficiency and dispersionless directional transfer are realized between edge states, which leads to an ultrabroadband light coupling covering a 1 dB bandwidth of ≈320 nm in experiment (>400 nm in simulation), with a length (≈50 µm) ≈1/10 of that required in conventional adiabatic transfer approach. Moreover, the coupling strategy exhibits a low insertion loss (<1 dB), a low crosstalk (<−10 dB), and a great robustness against structural deviations (≈100 nm). Furthermore, complex functional devices including beamsplitter and multiple‐level cascaded networks are constructed for broadband light routing and splitting. This work preserves significant advantages simultaneously in extending the operation bandwidth to all of the optical communication bands and minimizing the footprint, which demonstrates great potential for large‐scale photonic integration and high‐speed information processing on chip.