Frank Koppens

Institut de Ciències Fotòniques

Hyperspectral imaging uses the full spectrum of light to provide detailed insights into nature and its behavior. These insights open a realm for manifold applications, including autonomous driving, environmental monitoring, healthcare, space exploration, and even agriculture and food

processing. Imaging from the infrared to the terahertz regime poses a technological challenge because it requires devices that are sufficiently efficient and sensitive over the entire range of the spectrum.

In a new study published in Nature Photonics, the research led by Prof. Koppens at ICFO and in collaboration with ETH reported on the development of a novel ultra-broadband photodetector capable of detecting light very efficiently in a spectral range that spans from the far-terahertz (100 μm wavelength, equivalent to 3 THz) to near-infrared (2 μm wavelength or 150 THz) and with a good continuous efficiency in the entire range, without any gaps.

The device is based on Twisted Double Bilayer Graphene (TDBG), which is made of two bilayer graphene stacks rotated or twisted by a large angle (15°) and has been recently shown to create their own intrinsic electric field without the need for extra electrodes that complicate the fabrication of regular bilayer graphene. This has opened prospects for broadband detection in scalable systems; however, to date, the light-detection capabilities of TDBG have not been tested. The ultra-broadband photodetector has been shown to have good internal quantum efficiency, enhanced photoconductivity by interlayer screening, and scalability of TDBG because no gates are needed to apply the electric field in order to obtain the electronic bandgap.