Robust and plug-and-play chip-based swept-source optical coherence tomography for industrial applications

Optical coherence tomography (OCT) is a high-speed, non-invasive volumetric imaging modality. Beyond its established clinical utility, OCT is attracting growing interest from industry. To enable widespread deployment in industrial environments, OCT systems must become cost-effective and more robust. Photonic integrated circuits (PICs) offer a promising path toward compact, low-cost, and maintenance-free OCT systems. Nevertheless, achieving mass-producible and robust PIC-based industrial OCT remains challenging, particularly regarding material selection for fully foundry-based fabrication and flexible integrated sample arms. Here, we present a silicon nitride/silicon/germanium PIC-based OCT design specifically for industrial applications. Our PIC integrates interferometers and photodiodes with a robust, low-loss evanescent coupling structure, all in a compact 0.36-mm 2 footprint. We incorporated the PIC into a microscopic swept-source OCT system to assess its imaging performance. High-resolution imaging of a smartphone camera was achieved. We also demonstrate contactless calibration of wafer thickness with an absolute error of less than 2 µm, and high-speed (~ 10 5 μm/s) measurement of photoresist height with a relative error below 0.12%. To further enhance system robustness, we packaged an angle-polished ball lens (BL) probe with the chip via a fused single-mode fiber. Using this BL probe, we demonstrate flexible sample arm integration in PIC-based OCT, enabling volumetric endoscopic imaging in confined industrial samples. By connecting with other modular blocks, such as lasers or data acquisition boards, our robust, plug-and-play PIC platform can facilitate widespread adoption of OCT systems in industry.