Engineering a silicon- photonic bimodal biosensor

Abstract

Biosensors are powerful analytical devices that integrate biological sensing elements with physicochemical transducers to detect and quantify specific analytes, offering wide-ranging applications in fields such as medical diagnostics, environmental monitoring, food safety, and drug discovery. Bimodal waveguide (BiMW) biosensors, an interferometric optical biosensor, proven to be one of the best optical biosensors based on their high sensitivity, real time detection and compact design. During its early development stages, early 2010's, the height of the bimodal waveguide was increased to induce interference between the fundamental and first-order modes. Later, in late 2010's, change in the width of the bimodal waveguide were introduced to induce this interference. Our novel design builds upon these advancements, focusing on optimizing some parameters, mainly the width of the bimodal biosensor, to enhance performance and sensitivity. Many attempts were simulated to get a high fringe visibility and to determine the reduction in the transmission monitor was due to reduce the input power or the change in the effective index in the sensing region. Then, we came out with a design with one input, to maximize the fringe visibility, and two output, to determine the source power fluctuation. Multiple changes in the parameters, such as the width and the offset of the input waveguide, were investigated. In addition, change in the width of the bimodal waveguide was also included in this experiment. Finally, we varied the gap between the two output bends. All these parameters were varied to get a higher fringe visibility and lead to better sensitivity. Moreover, we discovered that this design requires the sample to be placed on top of the bimodal waveguide, rather than on the sides. We concluded that the best design we can extract is the one with 120 rad/RIU cm.