Origins and Mitigation of Scattering-Related Propagation Losses in Suspended GaAs Waveguides for Quantum Photonic Integrated Circuits

Quantum photonic integrated circuits (QPICs) offer a promising path toward scalable quantum technologies. QPICs rely on the integration of many quantum photonic components and interconnecting optical waveguides for generation, manipulation, and detection of single photons. A key challenge in QPICs is the management and minimization of optical losses, which is particularly critical for single-photon applications. In this paper, we investigate optical propagation losses in strip waveguides within suspended gallium arsenide (GaAs) platforms, which can directly host deterministic single-photon sources but suffer high scattering-related losses. We systematically analyze different scattering loss contributions by investigating four key waveguide perturbation types: sidewall roughness, top surface roughness, surface particles, and suspension tethers. Our approach combines rigorous 3D finite-difference time-domain (FDTD) simulations with experimental measurements to decouple and quantify individual contributions to the total propagation loss. We study two suspended GaAs platforms operating at different wavelengths: an established 930 nm platform and an emerging 1300 nm platform in the telecommunication O-band. Based on our findings, we identify the dominant scattering loss mechanisms and propose novel design-time guidelines and concrete strategies to reduce the main loss contributions by factors of 2.5–5. These improvements are crucial for enabling complex QPICs directly within the native platform of the single-photon source, supporting advances in integrated quantum technologies.