Abstract
We studied a refractive index sensor that consists of two cascaded ring resonators and that works analogously to a Vernier-scale. We implemented it in silicon-on-insulator and experimentally determined its sensitivity to be as high as 2169 nm/RIU in aqueous environment. We derived formulas describing the sensor's operation, and introduced a fitting procedure that allows to accurately detect changes in the sensor response. We determined the detection limit of this first prototype to be 8.310(-6)RIU.
Highlights
Label-free photonic biosensors can perform sensitive and quantitative multiparameter measurements on biological systems and can contribute to major advances in medical analyses, food quality control, drug development and environmental monitoring
We studied a refractive index sensor that consists of two cascaded ring resonators and that works analogously to a Vernier-scale
We implemented it in silicon-on-insulator and experimentally determined its sensitivity to be as high as 2169nm/RIU in aqueous environment
Summary
Label-free photonic biosensors can perform sensitive and quantitative multiparameter measurements on biological systems and can contribute to major advances in medical analyses, food quality control, drug development and environmental monitoring. Silicon-on-insulator photonic chips can be made with CMOS-compatible process steps, allowing for a strong reduction of the chip cost by high volume fabrication These sensor chips can be disposable, meaning that the chip is only used once, avoiding complex cleaning of the sensor surface after use. In [4] a ring resonator sensor is presented that is made with mass fabrication compatible technology and that has a very low detection limit of 7.6 10−7RIU This sensor has a bulk sensitivity of 163nm/RIU, which is not exceptionally high. In [12] a sensor is introduced that consists of two cascaded ring resonators, and it is shown theoretically that it can obtain very high sensitivities thanks to the Vernier-principle It operates as a digital sensor which limits its smallest detectable shift and its detection limit. As stated in [12], the very large sensitivity of this sensor makes it very well suited for integration with on-chip dispersive elements such as arrayed waveguide gratings [15] or planar concave gratings [16], giving opportunities for cheaper and more portable sensor read-out
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