[PhD Thesis Presentation_Zoom]- Ms. Seyedeh Sahar Seyed Hejazi - "Atom-light interactions via evanescent fields"

Presentater: Seyedeh Sahar Seyed Hejazi

Supervisor: Professor Thomas Busch

Unit: Quantum Systems Unit

Title: Atom-light interactions via evanescent fields

Abstract:

Newly developed techniques for controlling and measuring quantum systems have recently created an interest in exploring how the presence of dielectric surfaces affects atomic systems. In this thesis, I present results obtained by studying how the presence of evanescent modes or an evanescent field emerging from a dielectric medium can affect different quantum system, such as one or two atom systems, or even multi-component Bose–Einstein condensates.

Evanescent fields are exponentially decaying fields which typically appear on the surface of dielectric systems, such as flat half-planes, optical nanofibers or prisms. By bringing atoms close to the dielectic surfaces, they can couple to the evanescent modes, leading to new effects stemming from their guided nature or the spatial inhomogeneity. In the first project I present results on how the dipole-dipole interaction between two atoms can be enhanced close to the surface, which causes changes in various quantities, such as decay rates and frequency shift. In particular, the coupling between two different atoms depends on the orientation of their respective electric dipole moments and their relative location, which can lead to directional propagation of information between atoms and an oscillatory the decay rate. For multi-level atoms placed in the vicinity of an optical nanofiber, the spontaneous emission rates become a function of the magnetic sub-levels and orientation of electric dipole moments of atoms, in addition to the dependence on the optical modes of the fiber.

In a second project I consider the interesting feature of atom-fiber systems that is known chiral emission, and calculate the resulting chiral force on the atom. I show that it depends on various modes of fiber as well as on the orientation of electric dipole moment of atom.

When going beyond small systems and considering Bose-Einstein condensates, these fields can also act as artificial gauge fields and I show how they affect the phase-separation phase transition in two-component condensates.