A new consortium of European researchers aims to drastically reduce the cost of chemical sensors. Most devices on the market that can detect organic compounds are large, expensive and break easily. Integrating a chemical sensor into a silicon-based circuit could make this kind of detection just as lightweight, durable and affordable as a silicon chip.
Although silicon substrates for these kinds of light-sensitive chips are a promising new area of engineering research, the task is easier said than done. This is where the consortium, REDFINCH, comes in.
Photonics—a term that marries photons and electronics—is the field of engineering that uses light to transmit information, much in the same way that is traditionally done with electrons in electrical engineering. Photonic integrated circuits (ICs) are not dissimilar from regular circuits except they’re built with materials that can “guide” light. In the case of chemical sensors, these circuits, which respond to light, are used to detect when a particular compound is present, such as in a gas leak. Other key applications include health monitoring and diagnosis, detection of biological compounds, and toxic gas monitoring.
This is important to stakeholders such as the massive petrochemical and dairy industries, both of which need affordable, small and efficient sensors to monitor the quality of their products. One of the best ways to make photonic sensors more cost-effective is to construct them with a substrate that has a vast infrastructure, namely, silicon. The challenge is that the type of organic compounds these sensors need often have absorption fingerprints in the mid-infrared range—a slice of the EMF spectrum that does not always play nice with photonic silicon ICs.
Although silicon is transparent at the mid-infrared range and has a high refractive index, both desirable qualities for passive sensors, the problem is that silicon does not efficiently emit light. This is the main problem REDFINCH seeks to solve. Certain types of lasers—quantum cascade and interband cascade—show enormous promise in emitting light in the infrared range. Integrating them into silicon photonic ICs could prove fruitful for developing the desired sensor tech.
The REDFINCH consortium was announced earlier this month by Leti, a research subsidiary of the public research organization CEA Tech, also known as the French Alternative Energies and Atomic Energy Commission. In 2016, Reuters named CEA number one among “The World’s Most Innovative Research Institutions.” CEA has its fingers in many pies and has previously worked on applications such as 3D printing with metal paste.
“Despite the mid-infrared wavelength region’s importance for a wide range of applications, current state-of-the-art sensing systems in the MIR tend to be large and delicate. This significantly limits their spreading in real-world applications,” said Jean-Guillaume Coutard, Leti instrumentation engineer. “By harnessing the power of photonic integrated circuits, using hybrid and monolithic integration of III-V diode and interband cascade and quantum cascade materials with silicon, the consortium will create high-performance, cost-effective sensors for a number of industries.”