A new optical device that splits light beams into modes, with each mode acting as an independent channel of information, could be used to pack hundreds of modes into a single optical fiber, increasing the amount of information the fiber can carry. The device splits a beam of light into the “shapes” it is composed of, similar to how a prism splits white light into different colors. It was developed by researchers at the University of Queensland and Nokia Bell Labs. Using common optical components — a spatial light modulator and a mirror — the researchers built a planar lightwave circuit (PLC)-based mode sorter capable of splitting a beam into a Cartesian grid of identical Gaussian spots, each containing a single Laguerre-Gaussian component. The mode sorter could be used to increase internet speeds and improve image quality, especially for medical imaging and images of space. Courtesy of Joel Carpenter. While spectral or polarization beamsplitting can be straightforward, said the researchers, the spatial decomposition can be more difficult, and few options exist regardless of wave type. The new device allows the spatial properties of light to be decomposed in 2D and with high dimensionality, enabling functionality in the spatial domain. The new mode sorter could be applied to improve internet speeds and image quality, said researcher Joel Carpenter. “Just as an image can be made by adding a bunch of pixels together, we can make an image or beam by adding together a bunch of these modes,” he said. “Some things are easier to detect if you look at the modes rather than pixels, because it is displaying the image in a different form. For example, modes could make it easier to detect an image of a planet orbiting a faraway star.” The research was published in Nature Communications (https://doi.org/10.1038/s41467-019-09840-4). Researchers from the University of Queensland and Nokia Bell Labs present a device that can split a beam of light into the beam “shapes” that it’s composed of, like a prism splits white light into its colors. Courtesy of Joel Carpenter/University of Queensland.