Laura Russell

Spectroscopy, Manipulation and Trapping of Neutral Atoms, Molecules, and Other Particles Using Optical Nanofibers: A Review

The use of tapered optical fibers, i.e., optical nanofibers, for spectroscopy and the detection of small numbers of particles, such as neutral atoms or molecules, has been gaining interest in recent years. In this review, we briefly introduce the optical nanofiber, its fabrication, and optical mode propagation within. We discuss recent progress on the integration of optical nanofibers into laser-cooled atom and vapor systems, paying particular attention to spectroscopy, cold atom cloud characterization, and optical trapping schemes. Next, a natural extension of this work to molecules is introduced. Finally, we consider several alternatives to optical nanofibers that display some advantages for specific applications.

Spectral distribution of atomic fluorescence coupled into an optical nanofibre

We analyse the lineshape of the fluorescence emitted by a cloud of optically excited cold atoms and coupled into an optical nanofibre. We examine the efficiency of the fluorescence coupling and describe the asymmetry of the lineshape caused by the redshifts arising from both the van der Waals and Casimir–Polder interaction of the atoms with the surface of the optical nanofibre. We compare the contributions of the van der Waals and Casimir–Polder redshifts and show that the lineshape of the fluorescence coupled into an optical nanofibre is, basically, influenced by the van der Waals redshift and is characterized by a long tail on the red side of the spectrum. We conclude that a measurement of the lineshape of the coupled fluorescence could be used to characterize the strength of the interaction of atoms with dielectric surfaces and for the detection of atoms using nanofibres.

Sub-Doppler temperature measurements of laser-cooled atoms using optical nanofibres

We present a method for measuring the average temperature of a cloud of cold 85Rb atoms in a magneto-optical trap using an optical nanofibre. A periodic spatial variation is applied to the magnetic fields generated by the trapping coils and this causes the trap centre to oscillate, which, in turn, causes the cloud of cold atoms to oscillate. The optical nanofibre is used to collect the fluorescence emitted by the cold atoms, and the frequency response between the motion of the centre of the oscillating trap and the cloud of atoms is determined. This allows us to make measurements of cloud temperature both above and below the Doppler limit, thereby paving the way for nanofibres to be integrated with ultracold atoms for hybrid quantum devices.

Investigation of a 85Rb dark magneto-optical trap using an optical nanofibre

We report here the first measurements on a dark magneto-optical trap (DMOT) of 85Rb atoms using an optical nanofibre (ONF) with a waist of ~1 μm. The DMOT is created using a doughnut-shaped repump beam along with a depump beam for efficient transfer of cold atoms from the bright hyperfine ground state (F = 3) into the dark hyperfine ground state (F = 2). The fluorescence from the cold 85Rb atoms of the DMOT is detected by coupling it into the fibre-guided modes of the ONF. The measured fractional population of cold atoms in the bright hyperfine ground state (p) is as low as ~0.04. The dependence of the loading rate of the DMOT on cooling laser intensity is investigated and also compared with the loading rate of a bright MOT. This work lays the foundation for the use of an ONF for probing a small number of atoms in an optically-dense cold atomic cloud.We have performed release-recapture temperature measurements of laser-cooled Rb-85 atoms using an optical nanofibre (ONF) in a magneto-optical trap (MOT). The effects of changing the cooling laser light-shift parameter on the temperature of the cold atoms and spring constant of the trap are studied. By varying the cold atom number density near the ONF, the onset of the multiple scattering regime is observed without the need for an estimation of the atom cloud size. Moreover, this sensitive ONF assisted release-recapture technique is easily able to detect any optical misalignment of the cooling laser beams in the MOT.

Release-recapture experiment of Cold 85 Rb atoms with an optical nanofiber probe

An optical nanofiber (ONF) has been used to measure the temperature of cold 85Rb atoms in a magneto-optical trap by the release-and-recapture method. Integration of the ONF with cold atoms is useful for quantum technologies.

Nanofiber optical interfaces for laser-cooled atoms

In this work we present results on the use of optical nanofibers of subwavelength diameter as interfaces for probing and manipulating laser-cooled rubidium atoms. In particular, we concentrate on photon counts emitted through the nanofiber.

Ultrathin Optical Fibers as Tools in Atom Optics

We present results obtained using a tapered optical fibre to probe the characteristics of a cloud of cold rubidium atoms. The atom cloud profile as a function of rubidium vapor pressure is studied.