The advancement in technology has led to the development of various fields and applications such as the artificial intelligence that require the use of various sensors based on their properties, functionality, and performance. The microring-resonator-based sensor, in particular, are used for several sensor application such as pressure, temperature, biosensors, gas sensors among others. These sensors have lightweight and size compact hence widely preferred. Together with other photonic sensors, they are built of silicon-on-insulator photonic devices with high refractive index and high-quality CMOS processing facilities.
Microring-based optical sensors work on the principle where the resonant wavelength of the resonator ring is shifted depending on the interaction between the measurand and the light that is confined inside the core due to the changing refractive index of the guided mode. The change in the measurand is then converted into a measurable signal by sensing interrogation method. The method involves either converting the wavelength shift into intensity variation or monitoring the wavelength shift directly.
These two methods are however faced by several other disadvantages apart from being bulky and expensive. For instance, optical spectrum analyzer (OSA) used in direct interrogation method is characterized by slow sweeping speed and requires the use of a high-resolution tunable laser which is much expensive. Therefore, there is a need for a cost-effective interrogation method for determining the amount of change in the measurand and conveying it into a detectable signal.
A group of researchers at the University of Sidney, Faculty of Engineering and Information Technology: Wenjian Yang, Shijie Song, Dr. Xiaoke Yi, Suen Xin Chew, Dr. Liwei Li and Dr. Linh Nguyen developed a novel cost-effective interrogation method for silicon-on-insulator (SOI) based sensitive integrated sensor. The sensor consisted of a single microring resonator. The proposed structure is capable of simultaneously measuring the optical powers for drop port and through port of the add-drop microring resonator through the help of a linear amplitude comparison sensing function (ACSF). This was in a bid of achieving a fast response sensing function and fully small-scale integrated sensors. Their research work has been published in the research journal, Optics Letters.
From the experimental results, the authors achieved an enhanced relationship between the ACSF value and the resonant wavelength shift. For instance, the R-squared value was approximately 0.99, which was confirmed in the demonstrated temperature sensor experiment.
The sensing performance of the proposed novel system was enhanced by the elimination of the effects of the unexpected power fluctuations of the input laser and the approximate representation of the linear relationship with the measurand. This was attributed to the contrast ratio of both the drop port and through port. The main advantages of the proposed silicon-on-insulator microring-resonator based sensor are the fast-linear response, high sensitivity, compactness and low cost. Through monolithic integration, a more convenient and compact sensor will be produced especially on large scale basis.
Yang, W., Song, S., Yi, X., Chew, S., Li, L., & Nguyen, L. (2018). Silicon-on-insulator microring resonator sensor based on an amplitude comparison sensing function. Optics Letters, 43(1), 70.Go To Optics Letters