Researchers from the University of Sydney developed a sensor capable of correcting the distortion of starlight caused by heat variations in Earth’s atmosphere. The sensor would allow ground-based telescopes to study habitable exoplanets. The technology builds on a method to measure and correct the wavefront of light as it passes through atmospheric turbulence directly at the focal plane of an imaging instrument. This is done using a photonic lantern, to convert light, that is linked to a neural network inference process. The researchers called the device a photonic wavefront sensor, which can be placed directly in the optical instrument where the image forms. In the photonics lab at the Sydney Nanoscience Hub, University of Sydney, from left: Alison Wong, Christopher Betters, Barnaby Norris, Sergio Leon-Saval. Courtesy of the University of Sydney. The device can measure and correct the distortion caused by the atmosphere using a telescope’s adaptive optics system thousands of times per second to produce a clear image. “This new sensor merges advanced photonic devices with deep learning and neural networks techniques to achieve an unprecedented type of wavefront sensor for large telescopes,” said Barnaby Norris of the University of Sydney. The technology will allow ground-based telescopes to image exoplanets orbiting distant stars from Earth. Over the past two decades, thousands of exoplanets have been detected, though seldom by ground-based instruments. “It is really hard to separate a star’s ‘twinkle’ from the light dips caused by planets when observing from Earth,” Norris said. “Most observations of exoplanets have come from orbiting telescopes, such as NASA’s Kepler. With our invention we hope to launch a renaissance in exoplanet observation from the ground.” The sensor will be deployed in the 8.2-m Subaru Telescope in Hawaii, operated by the National Astronomical Observatory of Japan. “This is no doubt a very innovative approach and very different to all existing methods,” said Oliver Guyon of the University of Arizona. “It could potentially resolve several major limitations of the current technology. We are currently in collaboration with the University of Sydney team toward testing this concept at Subaru in conjunction with SCExAO, which is one of the most advanced adaptive optics systems in the world.” According to Sergio Leon-Saval, director of the Sydney Astrophotonic Instrumentation Laboratory at the University of Sydney, the technique could prove useful in a wide range of fields including optical communications, remote sensing, and in vivo imaging. These applications each require the reception and/or transmission of accurate wavefronts through a turbulent or turbid medium, such as water, blood, and air. The research was published in Nature Communications (www.doi.org/10.1038/s41467-020-19117-w).
