Machine learning-assisted tomographic reconstruction of refractive index profiles for femtosecond laser-written waveguides

We report machine learning (ML)-assisted limited-angle tomographic measurements of waveguides in glass fabricated using femtosecond laser micromachining (FLM). First, we manufacture waveguides in thin glass via FLM, and their effectiveness as a single-mode waveguide is confirmed via light coupling and loss measurements. Second, ML-assisted limited-angle tomography is successfully employed to visualize and measure 3-D index profiles of the FLM-written waveguide and give valuable insights into its structure. Our ML-assisted tomography should provide an important and robust diagnostic for the fabrication of photonic devices via 3-D visualization.