Design of a silicon micro-ring resonator for improved optical bio-sensing sensitivity and selectivity

초록

We report on the successful design of a silicon micro-ring resonator for improved sensitivity and selectivity in the optical bio-sensing applications. By controlling the waveguide width w, the radius of the resonator R, and the waveguide separation S, we improved the sensitivity and the selectivity of the micro-ring resonator sensor. For this we calculated the sensitivity of the micro-ring resonator using a resonant equation. We found that the reduction of the width of the silicon waveguide made it possible to improve the sensitivity of the micro-ring resonator. In order to characterize the quality factor we used non-unitary transfer matrix method that we developed to analyze the micro-ring resonator. We found that the decrease of radius of resonator R and the increase of the separation S, made it possible to improve the selectivity. But this results in the decrease the coupling coeffi ciency of the micro-ring resonator. Too high a selectivity(>10,000) caused by low coupling coeffi ciency(<1%) limited the output intensity to less than 10% of the input intensity. From these results we were able to design the micro-ring resonator. We obtained the sensitivity as 7.9nm/0.001, which is a 50% increase over the sensitivity value without the reduction of the waveguide width. We obtained the selectivity of more than 3,000 with nearly 100% output intensity. We compared these results with the results obtained from the wellestablished Finite Difference Time Domain (FDTD) method and found that they are in excellent agreement with each other.