Transmission of the fundamental mode in multi-mode waveguides is an effective scheme for a silicon-based platform to reduce scattering loss. However, the application of the scheme is usually limited to straight waveguides and restricted in multi-mode bending waveguides. This is because the fundamental mode of a straight waveguide is seriously disordered after passing the bend. In this work, we have presented a “matched bending radius” approach, by which an ultra-low loss and negligible modal disorder have been demonstrated in the Si and Si₃N₄ multi-mode waveguides. The estimated TE₀ mode transmission factor is almost 0 dB at the matched bending radius, indicating that the fundamental mode can be re-generated after passing the multi-mode bending waveguide. The proposed approach will contribute to applying the low loss scheme in large-scale photonic integrated circuits.

多模波导中基模的传输是硅基平台减少散射损耗的有效方案。然而，该方案的应用通常仅限于直波导和多模弯曲波导。这是因为直波导的基模在通过弯曲后严重紊乱。在这项工作中，我们提出了一种“匹配弯曲半径”方法，通过该方法在 Si 和 Si ₃ N ₄多模波导中证明了超低损耗和可忽略的模态紊乱。估计的 TE ₀在匹配的弯曲半径处，模式传输因子几乎为 0 dB，表明通过多模弯曲波导后可以重新生成基模。所提出的方法将有助于在大规模光子集成电路中应用低损耗方案。