Molding Optical Wavefronts Using Phase Discontinuities
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 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 in accordance with generalized laws of reflection and refraction. Plasmonic interfaces with spiral-shaped phase distributions generate optical vortex beams that carry orbital angular momentum.
Phase discontinuities enable wavefront engineering with unprecedented flexibility. I will discuss their implications for transformation optics, plasmonics, and optoelectronics, with a focus on mid-infrared and terahertz science and technology.
-Dr. Nanfang Yu