Reflected path enhanced absorbance in an integrated photonic sensor

Jianhao Shen; Daniel Donnelly; Swapnajit Chakravarty

doi:10.1117/12.2664033

13 June 2023 Reflected path enhanced absorbance in an integrated photonic sensor

Jianhao Shen, Daniel Donnelly, Swapnajit Chakravarty

Proceedings Volume 12532, Optical Waveguide and Laser Sensors II; 125320R (2023) https://doi.org/10.1117/12.2664033
Event: SPIE Defense + Commercial Sensing, 2023, Orlando, Florida, United States

Abstract

Evanescent wave sensors in photonic integrated circuits have been demonstrated for gas sensing applications. While some methods rely on the distinctive response of certain polymers for sensing specific gases, absorption spectroscopy identifies any gas uniquely from their unique vibration signatures. Based on the Beer-Lambert principle, the sensitivity of absorption by a gas on chip relies on the length of the sensing region, the optical overlap integral with the analyte gas and the absorption cross-section at the wavelength with the fundamental vibration signature. The overlap of the optical mode with the analyte has been enhanced in photonic devices by combining slot waveguide confinements with photonic crystal slow light effects. While the absorption cross-section is a property of the gas, the length of the sensing region is limited by the available area on a chip and waveguide propagation losses that limit the minimum signal to noise ratio. In this paper, we show that by incorporating reflecting loop mirrors, the absorption path length can be doubled for the same geometric length of the absorption sensing waveguide. Light from a waveguide is split into two paths, each with a slow light photonic crystal waveguide, by a 2×2 multimode interference (MMI) power splitter. Each path is terminated by a loop mirror that causes the light to retrace its path back down the sensing arms thereby doubling the optical path length over which light interacts with the analyte. Results on the enhancement of phase sensitivity and absorbance sensitivity in the interferometric configuration are presented.

Conference Presentation

Citation Download Citation

Jianhao Shen, Daniel Donnelly, and Swapnajit Chakravarty "Reflected path enhanced absorbance in an integrated photonic sensor", Proc. SPIE 12532, Optical Waveguide and Laser Sensors II, 125320R (13 June 2023); https://doi.org/10.1117/12.2664033

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