A study on refractive index sensors based on optical micro-ring resonators

In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of Δn/n≈3×10⁻⁴, assuming that the experimental setup can detect relative wavelength shifts of the order of Δλ/λ≈3×10⁻⁵. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of Δn≈10⁻³ for a layer thickness of t=10 nm, and changes in the layer thickness of the order of Δt≈0.24 nm, for a refractive index change of Δn=0.05.