Pinças nano-ópticas e síntese enantiosseletiva com meta-estruturas.

Abstract

Research on chiral plasmonics and optical metamaterials has recently expanded the limits of the nano-optical tweezers (NOTs). High-efficiency plasmonic NOTs that trap molecules and nanonoparticles are now able to select chiral nanoparticles due to the introduction of chiral electromagnetic fields (CEFs). Plasmonic and metamaterials systems with intrinsic chirality, in general, can provide enhanced optical chirality factors, in addition to strong chiral light confinement. However, it is not clear what the operating limits of these devices are in relation to the size and chirality parameter of the trapped nanoparticle. In this sense, in this doctoral thesis, through electromagnetic simulations and semi-analytical calculations, three nanostructured systems were proposed and designed that address the plasmonic operating limitations mentioned above. First, a multi-resonant PNO based on coaxial plasmonic nanoapertures with elliptic symmetry was proposed to trap small Au and Si particles up to 1 and 1.5 in radius, respectively, and proteins up to 3 nm in radius using only the dipolar resonance mode. These conditions were reached when the incident electric field is parallel to the semi-major axis of the elliptical nanoaperture with an eccentricity of 0.93. Quadrupolar and sextupolar resonance modes also manage to efficiently capture nanoparticles and proteins with radii greater than 1.5 and 3 nm in radius, respectively. Second, an enantioselective PNO was proposed for chiral macromolecules with a radius of 5 nm and a chirality parameter of up to ±0.005. For this case, an asymmetric plasmonic nanoaperture excites with circularly polarized light was used. Optical enantioseparation of these spherical macromolecules with small chirality parameters was only possible thanks to the introduction of non-enantiomorphic CEQs generated at the tips of the asymmetric nanoaperture. Finally, inspired by the CEQs, it was developed a general semi-analytic method to find the T scattering matrix for multilayer spherical meta-structures in order to generate, manipulate and intensify these CEQs.