Numerical and Experimental Methods for Estimating the Propagation Loss in Microphotonic Waveguides

The accurate estimation of propagation loss in microphotonic waveguides is a crucial factor in the performance optimization of photonic integrated circuits. This article presents a comprehensive review of both numerical and experimental methods used to estimate propagation loss. Numerical methods, including volume current, finite-difference time domain, finite element, and eigenmode expansion, offer high precision by modeling the intrinsic physical characteristics of waveguides, such as sidewall roughness, which significantly contributes to scattering loss. However, these methods are heavily dependent on detailed physical measurements, including roughness profiles. In contrast, experimental approaches like the cut-back method and interferometric techniques provide practical means for measuring propagation loss in real-world settings. These methods, while simpler and faster, are limited in their capacity to explain the origins of propagation loss. The synergy between numerical and experimental techniques is critical to developing effective strategies for minimizing loss in advanced photonic integrated circuits. The findings of this study highlight the necessity for continuous improvement in both computational and experimental methods to enhance the performance of microphotonic waveguides.