Wafer-scale statistical extraction of parallel waveguide spacing from optical resonant spectra

In this work, we present a precise and scalable method for extracting the process parameter of parallel waveguide spacing in photonic integrated circuits. Channel-ring resonators with high sensitivity to fabrication variations are designed, and wafer-scale optical measurements are performed to acquire their transmission spectra. Based on a compact model linking microring geometry to spectral response, we quantitatively extract the effective waveguide gap. By correlating each resonator's position on the wafer, a virtual wafer map is generated to visualize the spatial distribution of fabrication-induced variations. Multiple resonator arrays with diverse design configurations are fabricated on a silicon photonics platform to experimentally validate the approach. The results demonstrate high extraction accuracy and statistical robustness, offering a viable route for in-line process monitoring and variation-aware modeling in photonic chip manufacturing.