Multifunctionality in Silicon Photonics Through Temperature‐Driven Inverse Design

ABSTRACT

The scalability of programmable photonic systems relies on compact, low‐loss, and reconfigurable building blocks capable of supporting multiple optical functions. While silicon photonics offers several tunability mechanisms, many existing approaches rely on resonant architectures, extended interferometric paths, or heterogeneous functional materials that increase footprint, sensitivity, or process complexity. Here, a temperature‐dependent co‐optimization framework is applied that embeds thermal reconfigurability directly into the inverse‐design process, enabling multiple optical functionalities within a single device geometry. Using adjoint‐based topology optimization together with the intrinsic thermo‐optic response of silicon, a compact optical switch with a µm ² footprint and a reconfigurable TE ₀ –TE ₂ mode converter occupying µm ² have been designed as representative devices and experimentally verified. Both devices exhibit low insertion loss, < 2 dB, and clear thermally programmable behavior, with good agreement between numerical and experimental results. This approach establishes a general, CMOS‐compatible route toward dense, multifunctional programmable photonic circuits.