Three Dimension Refractive Index Characterization for Photonic Waveguides

The nondestructive volumetric imaging technique to characterize a three-dimensional (3D) refractive index (RI) profile quantitatively is an essential tool for designing, fabricating, and evaluating photonic structures of various devices. Conventional 3D RI imaging methods usually depend on the sample rotation scheme, which finds it difficult to measure the RI distribution of sheet-like on-chip structures. In this study, we proposed an optical diffractive tomography (ODT) system by employing a galvanometric scanner to reconstruct on-chip waveguide RI profiles; the measured volumetric RI dimension was 63 × 63 × 32 μm ³ in a single measurement, and the RI sensitivity was up to 0.0015. The reliable reconstruction results proved that the proposed ODT system is a promising tool for quantitatively retrieving RI profiles of photonic devices.