Highly-Sensitive Unbalanced MZI Gas Sensor Assisted With a Temperature-Reference Ring Resonator

• Published in: IEEE photonics journal Vol. 14; no. 6; pp. 1 - 9
• Main Authors: Taha, Ayat M., Yousuf, Soha, Dahlem, Marcus S., Viegas, Jaime
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.01.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Gas flow; Gas sensors; Mach-Zehnder interferometer; Mach-Zehnder interferometers; Optical ring resonators; Optical sensors; Optical variables control; Optical waveguides; Rare gases; Resonators; ring resonator; Sensitivity; Silicon; silicon photonics; silicon-on-insulator; Temperature measurement
• ISSN: 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2022.3215713

In this paper we study the gas sensing performance of a compact silicon photonics Mach-Zehnder interferometer (MZI) with a coiled sensing arm. A partially exposed sensor was fabricated using deep UV lithography, with a process resolution of 248 nm. Testing with inert gases, He and N <inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>, resulted in a measured sensitivity and limit of detection of <inline-formula><tex-math notation="LaTeX">\sim 1458</tex-math></inline-formula> nm/RIU and <inline-formula><tex-math notation="LaTeX">\sim 8.5\times 10^{-5}</tex-math></inline-formula> RIU, respectively, in a sensing volume of 1.852 picoliters. The temperature sensitivity of the sensor was 166 pm/° C and the inclusion of a cladded ring-resonator, post-MZI, allowed resolving the temperature drift due to gas flow. In order to further enhance the overlap of the optical mode with the measurand and thus the sensitivity, a suspended MZI was designed and simulated with an expected sensitivity of <inline-formula><tex-math notation="LaTeX">\sim 5500</tex-math></inline-formula> nm/RIU, for wavelengths around 1550 nm and a temperature of 300 K.