The sCENT project has delivered a series of important scientific and technological breakthroughs in the field of trace gas sensing, with a clear focus on achieving ultra-sensitive, selective, and compact on-chip sensors capable of reaching parts-per-billion (ppb) detection limits. Early efforts focused on the development of silicon slot waveguides for methane detection, leading to a detection limit of 300 ppb, which already marked a new benchmark in integrated photonic gas sensors. However, challenges related to humidity-induced losses prompted a shift toward thin-film membrane waveguides, which ultimately revolutionized the field. The first-generation thin-film membrane waveguides demonstrated for the first time that waveguide-based gas sensing can exceed the interaction strength of free-space optical beams. Building on this success, the second-generation devices, incorporating metamaterial cladding, achieved unprecedented detection limits of 300 ppb for methane and 20 ppb for carbon dioxide. These figures represent improvements of two and five orders of magnitude, respectively, over the previous state of the art. The technology's high sensitivity also enabled the first demonstration of isotope ratio detection using an integrated photonic device—an achievement that paves the way for new capabilities in environmental monitoring and analytical chemistry.
Parallel to the waveguide innovations, the project also made notable progress in developing functional materials for gas enrichment on the chip surface. Collaborative work with ENS Lyon led to the successful synthesis of fluorinated cryptophane derivatives and their incorporation into spin-coated enrichment layers. These layers demonstrated the ability to concentrate methane when tested via Raman spectroscopy, representing a promising path toward integrating pre-concentration directly with spectroscopic detection. While full integration with waveguides has not yet been realized, this foundational work offers a strong basis for continued research and development beyond the scope of the original project.
Overall, the sCENT project has not only met but exceeded its core objectives by advancing on-chip spectroscopy to levels of sensitivity and selectivity previously achievable only with bulky laboratory instruments. These accomplishments are the result of a cohesive interdisciplinary effort spanning photonics design, materials science, and molecular chemistry. The work has been published in top-tier journals, including Light: Science & Applications (2021), where we first demonstrated that waveguides can provide stronger light-matter interaction than free-space beams, and Optica (2024), showcasing world-leading performance in gas spectroscopy on a chip. These contributions have already received considerable academic attention and also earned the prestigious Tycho-Jægers Prize in Electrooptics 2024, highly recognised in Norway. Project's impact is further evidenced by filing a patent for the waveguide platform, other high-profile scientific publications, and successful follow-up funding through an ERC Proof of Concept grant and national innovation programs. Collectively, these results underscore the project's high potential for real-world deployment and commercialisation.
