Influence of dimensional fluctuations on the optical coupling between nanobeam twin cavities

In this paper, we study the influence of fabrication uncertainties on silicon-on-insulator optical nanosystems performances. The considered structure consists in near-field coupled twin nanobeam cavities. We have performed experiments on a given population of samples, and noticeable changes in light propagation and localization were observed. Thanks to an analytic coupled-mode-based method supported by three-dimensional numerical computations, we quantitatively explain these experimental observations. We have indeed noticed that a few percent variation of the system nominal dimensions is enough to significantly change the optical coupling conditions between the cavities. Particularly, we show that, under specific conditions, light can stay locked in one of the two cavities. This result highlights the issues of reproducibility and reliability concerning future industrial application, like nano-optical electromechanical systems.