Second order effects of aspect ratio variations in high sensitivity grating couplers

In the following article we present our developments on how the geometrical parameters modify a grating-coupler sensitivity. Different sensors were fabricated, starting from the thin grating approximation (TGA), where the grating thickness is deprecated. Then, these devices were modified by varying etching depths and duty cycles. The sensors were modeled utilizing the equivalent layer approximation (ELA), and then the coupling angles were measured in the optical bench, showing an excellent agreement between model and reality. The same approximation was used to investigate how to improve the sensitivity of these devices. Another focus of attention was the integration of screen SiO2 layers over some grating paths for in-coupling and reference purposes. (c) 2007 Elsevier B.V. All rights reserved.