Reflectivity- losses compromise on the basis of a Bragg filter with high index modulation

In this article the authors explain the necessary compromise that should be attained between gain and losses by examining the impact of corrugation depth 1 on the reflectivity R and the losses of a Bragg Gratings-based optical filter, achieved by the technique of Focused Ion Beam (FIB). We demonstrate that if an optimal corrugation depth is achieved the filtering function of the device gets a high degree of performance. Indeed, we have been able to experimentally measure this (optimal) depth on several constructed structures and show that once the reflectivity reaches its maximum value, it is contre-productive to exceed this value of depth. In point of fact, we found out that going beyond this value causes an increase of the losses (related to the BG), and does not improve the reflectivity any further. The augmentation of losses degrades the transmission quality by giving rise to an increase of error probability and a lowering down of the bit rate.