On-Chip Silicon Bragg-Grating-Waveguide-Based Polymer Slot for Gas Sensing

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Physics Department

Second Author's Department

Physics Department

Third Author's Department

Physics Department

Fourth Author's Department

Physics Department

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https://doi.org/10.3390/photonics12060608

All Authors

Merna Khafagy Maira Khafagy Passant Hesham Mohamed A. Swillam

Document Type

Research Article

Publication Title

Photonics

Publication Date

6-1-2025

doi

10.3390/photonics12060608

Abstract

This work presents a novel (Formula presented.) gas sensor based on a slotted polymer-phaseshift Bragg grating (SP-PSBG) waveguide filled with polyhexamethylene biguanide (PHMB) as the sensing medium. The transmission resonance, characterized by a narrow peak with a full width at half maximum (FWHM) of 1.6 nm within the Bragg grating bandgap, is highly responsive to refractive index changes in PHMB caused by variations in (Formula presented.) concentration. Numerical simulations demonstrate a sensitivity of 14.4 pm/ppm, outperforming conventional gas sensors based on functional material coatings. This enhanced performance comes from the direct interaction between the PHMB-filled resonant structure and the cladding that contains (Formula presented.) molecules, eliminating the need for polymer-coated cladding layers. The optimization approach employed in this design focuses on maximizing the optical confinement factor within the PHMB-filled slot, leading to an effective overlap between the guided optical mode and the sensing material.

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