The French Atomic Energy Commission’s Electronics and Information Technology Laboratory (CEA-Leti) has developed a prototype of a next-generation optical chemical sensor using mid-infrared silicon photonics technology that can be integrated into smartphones and other portable devices.
Mid-infrared chemical sensors operate in the spectral range of 2.5–12 μm and are considered at the forefront of innovative silicon photonic devices. In less than a decade, chemical sensing has become one of the key applications of these devices due to their growing potential in spectroscopy, materials processing, chemical and biomolecular sensing, as well as security and industrial applications.
Measurements in the mid-infrared spectral range provide highly selective, sensitive, and definitive chemical identification capabilities.
CEA-Leti's coin-sized on-chip sensor prototype combines high performance and low power consumption, making it ready for IoT applications. It can be used in various consumer applications such as smart homes and vehicle air quality monitoring, as well as wearable health applications. Its industrial applications include real-time air quality monitoring and a wide range of worker safety applications.
Currently available mid-infrared optical sensors are typically large and expensive. Meanwhile, miniaturized and inexpensive sensors cannot meet the accuracy, selectivity, and sensitivity requirements of consumer applications.
While size and price are not the most critical issues for industrial applications, bulky and expensive optical sensors are a major obstacle for consumer applications, which require wearability and integration into a variety of portable devices.
“Mid-infrared silicon photonics technology has enabled a new class of integrated devices, achieving chip-level integration of the main building blocks required for chemical sensing,” said Sergio Nicoletti, the first author of the paper “Miniaturization of Mid-Infrared Sensors on Silicon: Challenges and Prospects” presented by CEA-Leti at SPIE Photonics West 2019.
CEA-Leti's breakthrough combines three existing technologies needed to manufacture on-chip optical chemical sensors: integrating mid-infrared lasers on silicon wafers; developing photonic integrated circuits (PICs) in the mid-infrared wavelength range; and miniaturizing photoacoustic detectors on silicon chips.
“While other R&D efforts have yielded similar results, the main achievement of our project lies in the use of equipment and processes typical of the IC and MEMS industries,” Nicoletti said. “Our focus on architecture and process selection, as well as the specific connections between a series of steps, were also crucial for the development of this optical chemical sensor, which CEA-Leti has now implemented as a demonstration prototype.”
