Researchers at the Harvard John A. Paulson School of Engineering and Applied Science have developed metasurfaces capable of manipulating the polarization of light with an unprecedented degree of control. “This research shows that the ability to switch between holographic images that need not be limited to just two polarization states,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the research paper. “Our new metasurface can encode an unlimited number of holographic images or manipulate light in virtually infinite number of directions based on a very large number of polarization states.” When illuminated with a laser light, the metasurface hologram implements a far-field in which light is directed on the basis of its incident polarization state. Here, the far-field measured on a digital image sensor reflects this desired behavior for six incident polarization states. Courtesy of the Capasso Lab/Harvard SEAS. The research demonstrates a new way to control polarized light with metasurfaces, in which researchers engineer a holographic image with a polarization tunable response across the image itself. The approach, the researchers said, could lead to applications in diverse fields including imaging, microscopes, displays, and astronomy. “This advancement is general and could be applied to almost any kind of optical system that uses polarized light,” said Noah Rubin, a postdoctoral fellow at SEAS and first author of the paper. “Specifically, this suggests that metasurfaces could be used in new types of laser systems whose output light could be engineered based on light’s polarization state, or perhaps even in telescope systems where similar types of optics are already being used to aid in the detection of Earth-like exoplanets.” “Holography has always been a popular technique to record and display information,” said Aun Zaidi, a graduate student at SEAS and co-lead author of the paper. “We have taken a fundamental principle of holography and generalized it in a way that greatly expands the information capacity of this rather old technique.” The researchers plan to study the devices further to understand how they may be applied to real-world applications. The research was published in Science Advances (www.doi.org/10.1126/sciadv.abg7488).