An intelligent sensor, the size of about 1/1000 of the cross-section of a human hair, has been developed that can detect the polarization, intensity and wavelength of light simultaneously using quantum properties of electrons. It is a significant development in the fields of healthcare, astronomy and remote sensing.
Artistic rendering of the intelligent sensing process: quantum geometric properties determine the photoresponses, which are then interpreted by a neural network. Image Credit: Xia group.
The research was headed by Fengnian Xia, the Barton L. Weller Associate Professor of Engineering and Science at Yale, and Fan Zhang, Associate Professor of Physics at the University of Texas at Dallas. The findings were published in the journal Nature.
In recent years, scientists have discovered that twisting a few materials at specific angles can produce “moiré materials,” which have previously unknown properties. The researchers built their sensing device out of twisted double bilayer graphene (TDBG), which is two atomic layers of natural stacked carbon atoms with a slight rotational twist.
This is important because the twist decreases crystal symmetry, and materials with less symmetrical atomic structures — in many cases — have some promisingly interesting physical properties not found in materials with greater symmetry.
The scientists were able to identify a strong presence of the bulk photovoltaic effect (BPVE), a process that transforms light into electricity and produces a response that is highly dependent on the light intensity, polarization and wavelength, using this device. The scientists found that external electrical means can further tune the BPVE in TDBG, allowing them to create “2D fingerprints” of photovoltages for each different incident light.
A convolutional neural network (CNN), a kind of artificial neural network earlier used for image recognition, was used to decipher these fingerprints, according to Shaofan Yuan, a graduate student in Xia’s laboratory and co-lead author of the study. They were able to demonstrate an intelligent photodetector from there.
Due to its small size, it could be useful for deep space exploration, in situ medical tests and remote sensing on autonomous vehicles or aircraft. Furthermore, their research opens up a new avenue for studying nonlinear optics using moiré materials.
Ideally, one single intelligent device can replace several bulky, complex and expensive optical elements that are used to capture the information of light, dramatically saving space and cost.
Chao Ma, Study Co-Lead Author and Graduate Student, Yale University
Chao Ma is a graduate student in Xia’s laboratory.
Theoretical calculations and analysis were performed by Patrick Cheung of the University of Texas at Dallas. Dr. Kenji Watanabe and Dr. Takashi Taniguchi of Japan’s National Institute for Materials Science are also contributing authors of the research.
Journal Reference:
Ma, C., et al. (2022) Intelligent infrared sensing enabled by tunable moiré quantum geometry. Nature. doi.org/10.1038/s41586-022-04548-w.