Measurements of the Effective Refractive Index of Bent Waveguide Based on Microring Resonators

The effective refractive index of waveguides is of great significance in optimizing the device structures and the integrated optical networks, as well as verifying and improving the fabrication processes. In this work, we propose and demonstrate a simple method for measuring the effective refractive index of bent waveguide on silicon on insulator (SOI) chip. By analyzing the troughs’ wavelength in the spectra of microring resonators (MRRs), the dispersion curves of four bent waveguides with corresponding radii have been accurately obtained. The numerical simulations show that the maximum measurement error of effective refractive index is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.7 \times 10^{-{5}}$ </tex-math></inline-formula> when the sampling wavelength interval is 0.02 nm. Through experimental and theoretical analysis, the maximum structural errors of waveguide width and height are 4.8 and 2.7 nm, respectively. It verifies the feasibility of this method and the accuracy of the manufacturing techniques used in the devices.