Conventional optical components such as lenses and holograms rely on gradual phase shifts accumulated during light propagation to shape optical wavefronts. It is possible to break away from our reliance on such propagation effects, and attain new degrees of freedom in optical design by introducing abrupt phase changes (“phase discontinuities”) into the optical path. This can be achieved by using the large and controllable phase shift between the excitation and radiated light of optical resonators such as plasmonic antennas.
In this talk I will show that meta-interfaces consisting of a two-dimensional array of optical antennas with spatially varying phase response and sub-wavelength separation can imprint an arbitrary distribution of phase discontinuities onto the propagating wavefront. A linear phase variation along the interface between two media leads to anomalously reflected and refracted beams that defy conventional laws of reflection and refraction. Plasmonic interfaces with spiral-shaped phase distributions generate optical vortex beams that carry orbital angular momentum. I will discuss the broadband and polarization properties of meta-interfaces and strategies to make them reconfigurable.
Meta-interfaces with phase discontinuities enable wavefront engineering with unprecedented flexibility. I will discuss their implications for optical technologies with a few examples.