Phys.org May 8, 2023
Metasurfaces have been rapidly advancing our command over the many degrees of freedom of light; however, so far, they have been mostly limited to manipulating light in free space. Metasurfaces integrated on top of guided-wave photonic systems have been explored to control the scattering of light off-chip with enhanced functionalities. However, these efforts have so far been limited to controlling one or two optical degrees of freedom at best. A team of researchers in the US (Columbia University, City University of New York) has developed leaky-wave metasurfaces, which are based on symmetry-broken photonic crystal slabs that support quasi-bound states in the continuum. This platform has a compact form factor equivalent to one of grating couplers, but it provides full command over the amplitude, phase, and polarization (four optical degrees of freedom) across large apertures. They developed devices for phase and amplitude control at a fixed polarization state, and devices controlling all the four optical degrees of freedom for operation at a wavelength of 1.55 μm. According to the researchers merging the fields of guided and free-space optics through the hybrid nature of quasi-bound states in the continuum, their leaky-wave metasurfaces may find applications in imaging, communications, augmented reality, quantum optics, LIDAR, and integrated photonic systems… read more. TECHNICAL ARTICLE
Full-wave simulations constructing the meta-unit library. Credit: Nature Nanotechnology (2023)Â