Meanwhile, in the Optical Sensors Lab of the Optics and Photonics Department, a research team achieved a QCL engineering breakthrough that could dramatically reshape continuous monitoring of chronic diseases. By integrating high‑performance mid‑infrared QCL sources onto silicon wafers through heterogeneous III‑V‑on‑Si bonding, they created a scalable, low‑cost platform capable of delivering compact, powerful optical sensors for everyday use.

​To improve the quality of life of people living with chronic diseases there is a need for continuous monitoring of certain physiological parameters. For example, blood glucose levels for diabetes, or blood pressure for hypertension," said Kevin Jourde, research engineer-optical instrumentation. “Our goal is to make these measurements as non-invasive and non-stigmatizing as possible. To achieve this, we are developing these sensors based on a QCL source.​

Singing Molecules

Badhise Ben Bakir, research engineer-QCL theme leader, noted that these lasers emit in the mid-infrared range, where molecules have a true absorption fingerprint.

Molecules 'sing' by absorbing specific wavelengths. That's their signature: the laser system reads it like a barcode. Our challenge is to create reliable, compact, and affordable sources manufactured at very large scale, he said.

To address these challenges, the 10-person team will develop micro-laser sources in CEA-Leti's cleanrooms, which use advanced microelectronics technologies.

'Thousands of Lasers on a Single Wafer'

These are the same technologies found in everyday high-tech devices. We use III–V materials, which are very efficient emitters of infrared light, unlike silicon," explained Marion Volpert, research engineer-process integration. "But in our case, we had to develop an innovative architecture, using heterogeneous integration—a key technology. This means assembling the III-V material onto silicon by molecular bonding. The advantage is that we can produce thousands of lasers on a single wafer and significantly reduce costs.

Badhise, who said the “smart" integration of III-V on silicon was a breakthrough, added that this integration approach also opens new design possibilities:

We design innovative architectures tailored to real-world applications. At CEA-Leti, we cover the entire value chain, from epitaxial materials to the final system.​

A Future Road Map

Looking head toward the wide spectrum of R&D possibilities, Maëva Doron, research engineer-optical sensors, said bringing complete QCL systems from the lab to everyday sensors requires key expertise in design and modeling, manufacturing, characterization and packaging.

“These miniaturized technologies open new application areas in infrared spectroscopy (and) these measurements are becoming more widely accessible and closely aligned with actual needs," she said. “For example, in healthcare, to measure blood glucose and other biomarkers; in industry, for process analysis and monitoring, including bioproduction; in environmental applications, to monitor air pollution levels and monitor greenhouse gas emissions or toxic substances. And looking further ahead, for plant monitoring."​

The Excitement​​​​​​​

​

Kevin Jourde, research engineer-optical instrumentation​

“The first time we saw light measured on the screen, it was already a huge moment for me​"                        

​​Marion Volpert, research engineer-process integration

“We switched on t​​he laser using the second architecture. The camera was completely saturated—there was so much light."

Maëva Doron, research engineer-optical sensors

“It was really the collective work of the team—ideas and energy of every single person—that brought us to that flash of brilliance."​

Badhise Ben Bakir, research engineer and QCL theme leader

“An alignment of planets, combined with the fresh perspective of young Ph.D. researchers constantly challenging us, is what allowed us to reach the performance levels we have ​today."​​​