Control of light at the nanoscale : from optical antennas to metamaterials

Abstract

Nano-optics is a rapidly developing area of modern physics. Research in this field aims to develop the processes and methods to control light properties on a subwavelength scale. In this Thesis we present our achievements on control of angular properties of artificially engineered structures. Our results cover the fields of optical antennas, metasurfaces and metamaterials. Chapter 2 is dedicated to the research of single nanoscale objects - optical antennas. We engineer angular response of an emitting antenna and achieve for the first time the control over the spin of emitted photons. In particular, photon-spin degeneracy was removed in photoluminescence of CdSe quantum dots coupled to nanoantennas. Photons with opposite spins were attributed to different wave-vectors. Our results on spin-controlled light emission open a new efficient route toward spincontrolled photonics with a range of possible applications in molecular detection, quantum light sources, or display technologies. In Chapter 3 we present the results of study of two-dimensional arrays of nanoscale elements - metasurfaces. We develop a general formalism that predicts the angular properties of metasurfaces based on their symmetry and level of disorder. In particular, we introduce the concept of quasicrystalline metasurfaces, which combines the advantages of both periodic and disordered structures, while mitigating their individual disadvantages. Our research opens up a new route toward flat and extremely thin optical devices. Chapter 4 describes our study of angular dispersion of three-dimensional nanostructured materials - metamaterials. We reports on several world-first experimental demonstrations supported by both theoretical results and numerical simulations, which includes the first example of a magnetic hyperbolic metamaterial, a direct observation of a topological transition between elliptic and hyperbolic regimes, and the first demonstration of the manifestation of strong effects of spatial dispersion. In Chapter 5 we discuss novel regimes of nonlinear wave-mixing in nanostructures with the emphasis on different scenarios of angular excitation. In particular, we demonstrate a dramatic enhancement of second-order nonlinear response in optical nanostructures. In contrast to conventional nonlinear media, the artificially engineer structure shows strong magnetic nonlinearities. We achieve an interference between electric and magnetic nonlinear responses of the nanostructure that can be either constructive or destructive depending on the particular scenario of angular excitation. The interference between the electric and magnetic nonlinear contributions allows for the control over the directionality of nonlinear processes. Show more