Revolutionary Nanophotonic Sensor Developed at TU Eindhoven Detects Ultrafine Particles with Unprecedented Sensitivity

ENGINEERINGNET.BE – Inhaling ultrafine particles (UFPs) can pose serious health risks.

To prevent this, proper methods of detecting UFPs and thus monitoring air quality are needed. Best through small, compact, accurate and cheap tools.

To this end, TU Eindhoven developed a nanophotonic sensor that is sensitive to minuscule changes in the environment around the sensor. So much so that he finds one nanoparticle. The sensor includes a semiconductor chip, which is placed on the tip of the fiber optic.

The sensor works based on a photonic crystal, a periodic structure that can reflect light in all directions. “An anomaly has been added to this crystal: a ‘photonic crystal cavity’ (PhCC),” said PhD student Arthur Hendriks from TU Eindhoven.

This ensures that light can be trapped in the crystal for a longer period of time. Hendriks: “So light is confined in a volume that is less than 1 µm3. This is called mode size, and it must be very small to measure tiny nanoparticles. “

The researchers were able to place the PhCC on the tip of the fiber using a method previously developed by TU Eindhoven. When a small particle approaches the PhCC in the crystal, it disturbs the cavity by changing the refractive index. “So the small particle changes the wavelength of the cavity, and we measure this change.”

“Our design offers unprecedented sensitivity compared to previous technologies,” says Hendriks. “Using the sensor, we were able to detect individual UFPs as small as 50 nanometers in diameter in real time. “

The next step for Hendriks and his colleagues is to hang the cavities, so that the quality factor and connection efficiency are even higher. This could be the result of nanophotonic cavities with first class properties, which are still easily readable through the optical fiber.

“Our technique could be used to detect even smaller particles. Or in other applications such as single-photon emitters and nano-optomechanical sensors,” says Hendriks. “Even single biological molecules could be detected. “

The next step for the UFP sensor is the European LEARN project, which aims to monitor and evaluate air quality in schools. TU Eindhoven plans to continue working on the sensor and testing it as part of this project.