We demonstrate an all-dielectric metasurface operating in the terahertz band that is capable of engineering a reflected beam's spatial properties with high efficiency. The metasurface is formed from an array of silicon cube resonators which simultaneously support electric and magnetic dipolar Mie resonances. By controlling the interference between these modes, the amplitude and phase of a reflected wave can be arbitrarily controlled over a sub-wavelength area. We demonstrate the flexibility and utility of this metasurface by optimizing the surface to produce several reflected beam types including vortex and Bessel beams; the latter being useful for diffraction-free point-to-point

Spoof plasmon surfaces consisting of linear arrays of subwavelength grooves are proposed as a novel platform for THz sensing. The tightly confined spoof plasmons, coupled via an Otto prism setup, are sensitive to the refractive index of the dielectric filling the grooves. Phase jumps at spoof plasmon resonances are used as a readout response for refractive index sensing. An overall sensitivity of 0.49 THz RIU−1 with figures‐of‐merit as high as 49 are achieved.