While conventional metasurfaces manipulate free-space light, here we overview two nonlocal metasurface architectures capable of customizing their own surface emission. The first, called “thermal metasurfaces”, produce thermal emission with custom wavefronts and polarization within the narrow bandwidth of a critically coupled quasi-bound state in the continuum. We report the first demonstration of unidirectional, spin-selective emission, achieved with silicon-based metasurfaces. The second, called “leaky-wave metasurfaces”, scatter guided waves to free space. These devices represent a generalized replacement for grating couplers, having equivalent form factor but complete control over the amplitude, phase, and polarization.
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