Highly Sensitive Integrated Photonic Sensor and Interrogator Using Cascaded Silicon Microring Resonators

Silicon photonic sensors have formed a favorable platform for various sensing applications due to the great advantages of high-performance, compactness, and large-scale integration capability. However, interrogation systems for reading out the encoded sensing information from an integrated sensor are still bulky and inflexible for various portable applications. In this paper, we propose a monolithic silicon refractive index sensor and interrogator by utilizing the cascaded microring resonators. A novel dithering and bias scan interrogation technique is designed for highly sensitive refractive index sensing with a broadband light source. The reflective index for aqueous solutions of ethanol with different concentrations are measured in the experiment, verifying that the sensitivity of the sensor is 125.1 nm/RIU and the detection accuracy of the whole system is 7.76
$\boldsymbol{\times 10^{-6}}$
RIU. This integrated photonic sensor and interrogator will be a promising solution for large-scale applications in biological and chemical sensing scenarios.