EPFL · Science

EPFL Researchers Develop Real-Time Tunable Mid-Infrared Metasurfaces

Scientists at EPFL have created ultra-thin silicon structures capable of rapidly adjusting their interaction with mid-infrared light, a breakthrough for advanced communications, sensing, and quantum technologies.

Metasurfaces, nanoscale patterned structures, are being explored to control mid-infrared light, crucial for identifying substances and for free-space optical communications. However, most existing metasurfaces have fixed optical properties after fabrication.

Researchers at EPFL's Bionanophotonic Systems Laboratory (BIOS) have overcome this limitation using suspended crystalline silicon membranes. By introducing mobile electrical charges into the silicon, they can alter the metasurfaces' light response in real time without physical changes.

These new metasurfaces exhibit significantly improved optical performance, with key metrics over ten times better than previous mid-IR platforms using similar materials. This is attributed to reduced optical losses achieved by suspending the nanostructured silicon layer in air.

The team demonstrated two methods for tuning the metasurfaces: one using integrated micro-heaters to induce changes via electrical current thousands of times per second, and another using ultrafast laser pulses for changes on nanosecond timescales.

This rapid, real-time manipulation of light signals could enhance communication efficiency and allow sensors to adapt quickly to changing environments. The manufacturing techniques used are compatible with large-scale semiconductor production, ensuring scalability.

This work establishes a versatile platform for future mid-IR photonics, potentially enabling compact, low-power devices for optical communications, highly selective sensors for chemical and biological detection, and active radiative cooling technologies.

The combination of high optical performance and fast tunability also holds promise for advanced photonics applications requiring precise light control, such as quantum spectroscopy.

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