Photonic metasurfaces, a modern approach to designing optical components

Recent advances in nanotechnology have stimulated the development of new approaches across many major disciplines including photonics, energy harvesting and biophysics. During this colloquium, I will present a brief overview of my recent contributions to the field. In partic ular, I will discuss the development of ultrathin nanostructured optical components. The wavefront of light can be controlled without relying on gradual phase shifts accumulated during propagation (as in the case of classical refractive materials such as lenses or prisms), but instead with abrupt phase discontinuities introduced into the light path over the scale of a wavelength. We will consider interfaces decorated by resonant nanostructures to generalize the classical laws of reflection and refraction. The versatility of these interfacial phase discontinuities can be exploited to create interfaces that focus light, function as waveplates, and even generate optical vortices and Bessel beams.

Another class of metallic components such as plasmonic gratings and plasmonic lenses are routinely used to convert free-space beams into propagating surface waves and vice versa. So far, this approach has been limited to simple light beams, such as plane waves or Gaussian beams. I will present a powerful generalization of plasmonic structures to couple more complex wavefronts. The approach is based on the principle of holography: the coupler is designed as the interference pattern of a complex beam with a surface wave. Integrating these holographic plasmonic interfaces into commercial silicon photodiodes, we demonstrated on-chip selective detection the orbital angular momentum of light. Such detectors are potential components for future classical and quantum optical communication networks. We have also generalized this holographic concept to generate non-diffracting surface waves and plasmonic bottle beams.