Periodic Reporting for period 1 - ONAIR (On-chip quantum absorption spectroscopy in the infrared)
Reporting period: 2023-09-01 to 2025-08-31
More than 11% of global deaths are attributed to air pollution. To address this issue, the first step is to enhance pollution monitoring—both for identifying specific molecules and assessing personal exposure. Achieving this goal requires a widespread network of sensors capable of providing precise, real-time air quality mapping. However, current gas sensors remain limited in terms of precision, portability, and durability.
The ONAIR project aims to develop a novel on-chip photonic gas sensor based on unique quantum effects. This sensor is designed to offer the selectivity, miniaturization, and cost-effectiveness necessary to enable high-resolution air quality monitoring over large areas
The ONAIR project aims to develop a novel on-chip photonic gas sensor based on unique quantum effects. This sensor is designed to offer the selectivity, miniaturization, and cost-effectiveness necessary to enable high-resolution air quality monitoring over large areas
The main goal of the project was to demonstrate the Undetected Photon (UP) Sensing technique—an innovative quantum sensing approach—on a photonic chip. This technique constitutes the core principle of the gas sensor under development.
The UP sensing method was successfully implemented on a silicon photonic chip, achieving phase sensing of photons at a wavelength of approximately 2 μm while detecting only photons at 1.3 μm. This achievement represents the first demonstration of phase sensing based on undetected photons in an integrated photonic platform.
To enable this result, a novel optical circuit architecture for UP measurements was designed and realized, exploiting higher-order waveguide modes. A comprehensive theoretical model of the quantum processes occurring within the integrated circuit was also developed, providing both fundamental insights and applied outcomes relevant to sensor performance.
In parallel, to enhance the overall efficiency of the sensor, new chip designs were developed and fabricated to explore UP sensing with different materials, novel quantum light sources, and advanced circuit configurations. In particular:
• A new photon-pair source based on silicon-core fibers was experimentally demonstrated;
• Thin-film lithium niobate photon-pair sources compatible with mid-infrared UP measurements were designed and fabricated;
• Silicon nitride–based photon-pair sources and UP circuits were designed and fabricated for improved integration and versatility;
• On-chip cavity-based UP circuits were designed on silicon platforms, employing ring resonators for narrowband and efficient photon-pair generation and probing.
The UP sensing method was successfully implemented on a silicon photonic chip, achieving phase sensing of photons at a wavelength of approximately 2 μm while detecting only photons at 1.3 μm. This achievement represents the first demonstration of phase sensing based on undetected photons in an integrated photonic platform.
To enable this result, a novel optical circuit architecture for UP measurements was designed and realized, exploiting higher-order waveguide modes. A comprehensive theoretical model of the quantum processes occurring within the integrated circuit was also developed, providing both fundamental insights and applied outcomes relevant to sensor performance.
In parallel, to enhance the overall efficiency of the sensor, new chip designs were developed and fabricated to explore UP sensing with different materials, novel quantum light sources, and advanced circuit configurations. In particular:
• A new photon-pair source based on silicon-core fibers was experimentally demonstrated;
• Thin-film lithium niobate photon-pair sources compatible with mid-infrared UP measurements were designed and fabricated;
• Silicon nitride–based photon-pair sources and UP circuits were designed and fabricated for improved integration and versatility;
• On-chip cavity-based UP circuits were designed on silicon platforms, employing ring resonators for narrowband and efficient photon-pair generation and probing.
The main result is the experimental demonstration of the undetected photon measurement on a photonic chip. This result paves the way towards a new generation of efficient and miniaturized sensors for gas- and bio- detection and spectrometry. Once fully developed and engineered, this technology can open new perspectives to fields like environmental monitoring and healthcare. In fact, while portable sensors for gas detection are already available, they lack selectively and sensitivity, making them not suitable for precise monitoring of toxic molecules or pollutants. The perspective of our technology is to enable miniaturized, portable and affordable devices, compatible with customer electronics and mass production.
To advance the development of such technology, further research in terms of optimal materials and platforms is required. This is needed to extend the wavelength of operation at larger mid infrared wavelengths, where molecules are more responsive. Experiments with actual gas samples are also needed, to investigate the efficiency of the sensor when exposed to gases and to optimize the interaction between guided light and molecules to be probed. Furthermore, a detailed market analysis to identify the killer applications and markets of interests is crucial for the successful commercial deployment of the technology.
Other results of the project include new quantum sources, which will impact both the field of research and technology: on one side, providing new solutions to advance fundamental studies about quantum phenomena; on the other, offering novel photon pair sources compatible with quantum communication protocols running in metropolitan fiber networks.
To advance the development of such technology, further research in terms of optimal materials and platforms is required. This is needed to extend the wavelength of operation at larger mid infrared wavelengths, where molecules are more responsive. Experiments with actual gas samples are also needed, to investigate the efficiency of the sensor when exposed to gases and to optimize the interaction between guided light and molecules to be probed. Furthermore, a detailed market analysis to identify the killer applications and markets of interests is crucial for the successful commercial deployment of the technology.
Other results of the project include new quantum sources, which will impact both the field of research and technology: on one side, providing new solutions to advance fundamental studies about quantum phenomena; on the other, offering novel photon pair sources compatible with quantum communication protocols running in metropolitan fiber networks.