A new light source in the mid-infrared could help detect pollution

EPFL researchers have come up with a new medium-infrared light source capable of detecting greenhouse gases and others, as well as molecules present in a person's breath. The compact system, which looks like a tiny suitcase, contains only two parts: a standard laser and a photonic chip of a few millimeters. The search is detailed in an article published in Nature Communications.

The spectrum of the average infrared is particularly useful for scientists because in this range of wavelengths, light can detect particles playing an important role in the environment and human health. Until now, however, infrared laser systems have proven difficult to transport because they involved complex equipment, subject to damage.

The new technology, developed by researchers from EPFL, could change the game. The team took a commercially available fiber laser and combined it with a micrometer waveguide chip to reliably generate light waves in the mid-infrared spectrum. They then added a spectrometer to demonstrate the potential of this light source, successfully detecting the presence and concentration of acetylene, a colorless and highly flammable gas.

How it works?

The system uses a compact and robust fiber laser that emits light in a specific wavelength range. The beam is directed through a waveguide, measuring one micrometer (0.001 mm) and half a millimeter long, which can change the frequency of light as it pbades. The system produces light in the mid-infrared spectrum retaining 30% of the original signal strength. Researchers can even adjust the wavelength of light by adjusting the geometry of the waveguide.

"This device sets a new benchmark for efficiency," says Davide Grbadani, one of the authors of the paper. "This is the first time anyone creates a fully integrated spectroscopic laser source.It removes the tedious process of accurately aligning all parts of a conventional laser system."

The breakthrough came after the team refined key aspects of the system design – the waveguide geometry and materials, as well as the wavelength of the original laser source. "Developing such a simple, efficient and robust system involved a lot of design work," says Camille Brès, project coordinator and head of the Photonic Systems Laboratory, part of the School of Engineering. from EPFL.

On-chip spectroscopy

This breakthrough paves the way for miniaturized IR technologies, a range of wavelengths that scientists rarely work with. "Once we have developed the system, we will be able to see the on-chip detectors that scientists can easily perform in the field," Brès adds.

This technology is based on research conducted at the Laboratory of Photonic Systems, led by Camille Brès, and the Laboratory of Photonics and Quantum Measurements, led by Tobias Kippenberg (STI / SB).