Design of Bragg Grating Sensors Based on Submicrometer Optical Rib Waveguides in SOI

Abstract

A submicrometer integrated optical sensor based on Bragg gratings in silicon-on-insulator technology is theoretically proposed in this paper. The grating analysis is performed using a mixed numerical approach based on the finite-element method and coupled mode theory. The possibility to use third-order instead of first-order grating is discussed and performances compared, thus overcoming fabrication problems associated to submicrometer scale features. A detection limit of approximately 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> refractive index unit has been calculated for a 173-mum-long grating. Strategies to further improve this value have been discussed too. Finally, fabrication tolerances influence on optimized gratings has been investigated.