Design guidelines for optical resonator biochemical sensors

We propose a design tool for dielectric optical resonator-based biochemical refractometry sensors. Analogous to the widely accepted photodetector figure of merit, the detectivity D*, we introduce a new sensor system figure of merit, the time-normalized sensitivity S*, to permit quantitative, cross-technology-platform comparison between resonator sensors with distinctive device designs and interrogation configurations. The functional dependence of S* on device parameters, such as resonant cavity quality factor (Q), extinction ratio, system noise, and light source spectral bandwidth, is evaluated by using a Lorentzian peak fitting algorithm and Monte Carlo simulations to provide theoretical insights and useful design guidelines for optical resonator sensors. Importantly, we find that S* critically depends on the cavity Q factor, and we develop a method of optimizing sensor resolution and sensitivity to noise as a function of cavity Q factor. Finally, we compare the simulation predictions of sensor wavelength resolution with experimental results obtained in Ge17Sb12S71 resonators, and good agreement is confirmed.