Mid-IR chemical sensors operate in the spectral range of 2.5µm to 12µm and are considered to be at the cutting edge of innovative silicon-photonic devices. In less than a decade, chemical sensing has become a key application for these devices because of the growing potential of spectroscopy, materials processing, and chemical and biomolecular sensing, as well as security and industrial applications.
Measurement in this spectral range provides highly selective, sensitive and unequivocal identification of chemicals.
The coin-size, on-chip, IoT-ready sensors prototyped by Leti combine high performance and low power consumption and enable such consumer uses as air-quality monitoring in homes and vehicles, and wearable health and well-being applications. Industrial uses include real-time air-quality monitoring and a range of worker-safety applications.
Mid-IR optical sensors available on the market today are typically bulky and expensive. Meanwhile, current miniaturized and inexpensive sensors cannot meet consumer requirements for accuracy, selectivity and sensitivity.
While size and price are not the most critical concerns for industrial applications, bulky and costly optical sensors represent a major barrier for consumer applications, which require wear-ability and integration in a range of portable devices.
“Mid-IR silicon photonics has enabled creation of a novel class of integrated components, allowing the integration at chip level of the main building blocks required for chemical sensing,” said Sergio Nicoletti, lead author of a paper titled “Miniaturization of Mid-IR Sensors on Si: Challenges and Perspectives”, presented by CEA-Leti at this year’s SPIE Photonics West 2019.
“Key steps in this development extend the wavelength range available from a single source, handling and routing of the beams using photonic-integrated circuits, and the investigation of novel detection schemes that allow fully integrated on-chip sensing.”
CEA-Leti’s breakthrough combined three existing technologies necessary to produce on-chip optical chemical sensors: Integrating a mid-IR laser on silicon; developing photonic integrated circuits (PICs) in the mid-IR wavelength range, and miniaturizing a photoacoustic detector on silicon chips.
“While other R&D efforts have had similar results, our project’s key achievement is the use of tools and processes typical of the IC and MEMS industries,” Nicoletti said. “Our focus on the choice of the architectures and processes, and the specific linkage of the series of steps also were critical to developing this optical chemical sensor, which CEA-Leti is now realizing as demo prototypes"
