On-Chip Sensing System Employing Wavelength Splitting for Noise Suppression

Funding Sponsor

University of British Columbia

Author's Department

Physics Department

Second Author's Department

Physics Department

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https://doi.org/10.1109/JLT.2025.3549774

All Authors

Raghi El Shamy Mohamed Swillam Xun Li

Document Type

Research Article

Publication Title

Journal of Lightwave Technology

Publication Date

1-1-2025

doi

10.1109/JLT.2025.3549774

Abstract

In this work, we present a novel refractive index (RI) sensing system capable of suppressing optical phase errors (noise). Phase errors, for instance, due to process and temperature variations, limit the sensor's accuracy and limit-of-detection (LoD). The proposed system uses four loop-terminated Mach-Zehnder Interferometers (LT-MZI) to achieve wavelength splitting. LT-MZI allows us to tune the output spectrum using its directional coupler coefficients. Wavelength splitting occurs by the RI change, using two LT-MZIs with opposite wavelength sensitivities. By determining two independent parameters, namely the wavelength splitting and the average wavelength, the system can differentiate between phase changes due to medium index change and phase changes due to any other effects (noise), which maximizes the detection accuracy. This wavelength splitting cannot be achieved using the conventional Mach-Zhender Interferometer (MZI). Another two LT-MZIs with a quarter of the length are used to increase the detection range. This system is used to design a liquid sensor based on CMOS-compatible silicon-on-insulator (SOI) technology, operating in the near-infrared range. The SOI platform achieves high sensitivity to changes in the medium's refractive index and enables compact device designs due to its high index contrast. However, it is also susceptible to optical phase errors. Our proposed system effectively mitigates these errors, enhancing accuracy and LoD. Our designed sensor achieves an intrinsic LoD of 8e-4, and a sensitivity as high as 7890 nm/RIU with a sensing arm length of only 500 µm, which are 3 and 2 times higher than single MZI, respectively. In addition, this sensor has a much higher detection range, 6.3 times higher than a single MZI, and can suppress optical phase noise. Finally, our proposed system was fabricated and experimentally characterized, with measurements aligning closely with simulation results, verifying the reliability of our design.

First Page

5292

Last Page

5298

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