Efficient High Order Mode Supercontinuum Generation and Third-Harmonic Generation via Shortcut to Adiabaticity Coupling in Communication Band

This study pioneers the application of Shortcut to Adiabaticity (STA) technology for efficient high-order mode supercontinuum generation (SCG) and third-harmonic generation (THG) in Ta₂O₅-based nonlinear waveguides, specifically designed for the 1550 nm communication band. Using the Lewis-Riesenfeld invariant method, we developed an STA-based directional coupler that achieves over 85% coupling efficiency from the TE₀₀ to TE₁₀ mode, surpassing the bandwidth and length limitations of conventional couplers while maintaining robust broadband performance. Leveraging Ta₂O₅’s exceptionally high nonlinear refractive index—far exceeding that of Si₃N₄—we achieved broadband SCG spanning 1250 nm to 1900 nm with an ultralow pump energy of just 75 pJ. Additionally, we observed stable THG at 522 nm, confirmed through power dependence analysis, with remarkable conversion efficiency at only 83 pJ pulse energy—outperforming traditional Si₃N₄ waveguides by an order of magnitude. This synergy between STA's advanced coupling design and Ta₂O₅’s superior nonlinearity not only expands the frontiers of high-order mode nonlinear optics in the telecommunications regime but also establishes a transformative framework for compact, energy-efficient photonic integrated circuits, driving advancements in ultrafast and quantum optical applications.