Inverse Design of Integrated Terahertz Vortex Beam Emitters with Staged‐Annealing Topology Optimization

ABSTRACT Integrated photonics is increasingly demanded in applications such as large‐scale data centers, intelligent sensing, and next‐generation wireless communications, where compact, multifunctional, and energy‐efficient components are essential. Inverse‐designed photonics, empowered by optimization and learning algorithms, have emerged as a powerful paradigm for realizing compact and multifunctional integrated photonic components. In this work, we develop a staged‐annealing topological optimization (SATO) framework tailored for the design of integrated terahertz (THz) beam‐shaping devices. Employing this inverse‐designed framework, we experimentally demonstrate a class of compact THz vortex beam emitters on an all‐silicon on‐chip platform. These devices efficiently convert the in‐plane fundamental transverse electric (TE) waveguide mode into free‐space vortex beams with mode purity up to 87% and energy conversion efficiency up to 74% across the target wavelength range (680–720 µm). The inverse‐designed emitters exhibit ultracompact footprints (lateral size < 4λ) and a free‐standing configuration, enabling the generation of dual‐directional vortex beams carrying opposite topological charges. The proposed SATO framework provides a generalizable and fabrication‐compatible approach for THz photonic device engineering, offering a scalable pathway toward complex structured beam manipulation in next‐generation wireless communication systems and on‐chip integrated THz photonic systems.