A low-loss waveguide transition structure for photonics interposer across exposure field stitching boundary and design method

Abstract

This invention discloses a low-loss waveguide transition structure and design method for cross-exposure field splicing boundaries in photonic interposers. In this invention, a three-segment structure of "smooth gradient segment – ​​widened rectangular segment – ​​smooth gradient segment" is set near the splicing boundary, allowing the waveguide mode to expand appropriately at the boundary. This effectively alleviates the mode mismatch problem caused by splicing deviations, thereby significantly reducing insertion loss and improving optical signal transmission efficiency. A fifth-order polynomial smooth function satisfying triple continuity constraints of position, slope, and curvature is used to define the transition segment boundary, avoiding mode perturbations caused by geometric abrupt changes, significantly reducing reflection and scattering losses, and improving the integrity of optical signal transmission. Setting the splicing boundary within the widest widened rectangular segment of the waveguide, where the mode size is larger, significantly reduces the sensitivity to splicing deviations such as lateral misalignment, minute rotation, and local boundary discontinuities, thereby greatly improving the process tolerance to splicing errors.

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