Mark Sadgrove

Two port optical devices couple light to either port dependent on the input photon state. An important class of two-port devices is that of evanescently-coupled interfaces where chirality of photon coupling can lead to important technological applications. Here, we perform a fundamental characterization of such an interface, reconstructing the two-port polarization response over the surface of the Poincaré sphere for an optical nanofibre. From this result, we derive a chirality measure which is universal, obeying a one parameter scaling law independent of the exact parameters of the nanofibre and wavelength of light. Additionally, we note that the polarization response differs qualitatively for single and multiple coupled emitters, with possible implications for sensing and the characterization of waveguide coupled spins.

We propose a method of trapping atoms in arrays near to the surface of a composite nanophotonic device with optimal coupling to a single cavity mode. The device, comprised of a nanofiber mounted on a grating, allows the formation of periodic optical trapping potentials near to the nanofiber surface along with a high cooperativity nanofiber cavity. We model the device analytically and find good agreement with numerical simulations. We numerically demonstrate that for an experimentally realistic device, an array of traps can be formed whose centers coincide with the antinodes of a single cavity mode, guaranteeing optimal coupling to the cavity. Additionally, we simulate a trap suitable for a single atom within 100 nm of the fiber surface, potentially allowing larger coupling to the nanofiber than found using typical guided mode trapping techniques.

Nanophotonic devices are becoming increasingly important for enabling the controlled and efficient production of photons in well defined modes of optical resonators and waveguides. A particular class of such devices which has seen extensive application in recent years is that of evanescently coupled waveguides which can be used to create fiber-coupled single photon sources or to couple light to other nanophotonic systems. However, evanescent coupling typically results in equal intensities coupled to either port of the waveguide, leading to a 50% if it is desired to send photons to a particular receiver.

We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold ²³Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry.