A Highly Sensitive Refractometric Sensor Based on Cascaded SiN Microring Resonators

Abstract

We investigate a highly sensitive optical sensor based on two cascaded microring resonators exploiting the Vernier effect. The architecture consists of two microrings with a slight difference in their free spectral ranges. This allows the generation of the Vernier effect for achieving ultra-high sensitivities. The sensor chip was fabricated using a silicon nitride platform and characterized with isopropanol/ethanol mixtures. A sensitivity of 0.95 nm/% was found for isopropanol concentrations in ethanol ranging from 0% to 10%. Furthermore, a collection of measurements was carried out using aqueous sodium chloride (NaCl) in solutions of different concentrations, confirming a high sensitivity of 10.3 nm/% and a bulk refractive index sensitivity of 6,317 nm/RIU. A limit of detection of 3.16 × 10−6 RIU was determined. These preliminary results show the potential features of cascaded silicon nitride microring resonators for real-time and free-label monitoring of biomolecules for a broad range of applications.

Applications of Optical Microcavity Resonators in Analytical Chemistry

“…The simplest implementation of an optical resonator sensor is for bulk refractive index sensing using an unmodified sensor surface (46, 47, 95, 96). Unmodified sensors can also be used to monitor adsorption and/or desorption of an analyte onto the sensor surface, such as bovine serum albumin (BSA) (20, 30, 55, 57).…”

Microfluidic Whispering Gallery Mode Optical Sensors for Biological Applications

“…Generally, planar resonators are limited to a low detection sensitivity due to the low Q-factor caused by their direct contact with the substrate. As a result, several methods were proposed to increase the sensitivity, including employing slot waveguides, [106] using porous silicon resonators, [107] cascading the resonators, [108][109][110] amplifying signals through particle trapping, [111] etc.…”

Compact Inner-Wall Grating Slot Microring Resonator for Label-Free Sensing

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