Space-time metasurface makes light reflect only in one direction  December 20, 2019 Currently isolators and circulators based on the magneto-optic effect make the devices bulky and difficult for integration. Leveraging both spatial and temporal phase manipulation offered by an ultrathin nonlinear metasurface researchers at Pennsylvania State University experimentally demonstrated nonreciprocal light reflection at wavelengths around 860 nm. The metasurface creates spatial phase gradient and multi-terahertz temporal phase wobbling, which leads to unidirectional photonic transitions in both the momentum and energy spaces. They observed completely asymmetric reflections in forward and backward light propagations over a large bandwidth around 5.77 THz within a sub-wavelength interaction length of 150 nm. Their approach highlights a […]