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Exploring the limits of ultra-strong light-atom interaction in waveguide-trapped cold-atoms

Ashby Paul Hilton, Christopher Perrella, Fetah Benabid, Ben M. Sparkes, Andre Nicholas Luiten, P. S. Light

Published Feb 15, 2018• 1 citation
OpenAlex

Abstract

We have developed an atom-guiding technique that loads $3\times 10^6$ cold rubidium atoms into hollow-core optical fibre, an order-of-magnitude larger than previously reported results. This achievement was guided by a physically realistic simulation that led to an experimental loading efficiency of $3\%$, giving a peak optical depth of over $600$. The loading efficiency was limited only by the geometric overlap of the atom cloud an an optical guide beam, and we have identified techniques that would allows us to exceed this limit. We also present a fast and minimally destructive probing technique that enables us to follow the dynamics of the cold atom cloud as it falls into the fibre - this strengthens the confidence in our detailed model, and enables adjustment of the experiment into an optimal state. We are able to observe the effect of light-assisted cold atom collisions as well as background gas collisions in the fibre. The combination of these observations and physical understanding from the simulation allows us to estimate the ultimate limits to loading cold atoms into hollow-core fibres.

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High-efficiency cold-atom transport into a waveguide trap

Ashby Paul Hilton, Christopher Perrella, Fetah Benabid +3 more

Hollow-core optical fibers loaded with cold atoms show great promise as platforms for quantum information processing and highly nonlinear optics, but their limitations have remained poorly understood. Using detailed Monte Carlo simulation, the authors model the loading dynamics and predict the sensitivity of the system to various experimental parameters. Thus guided, they develop an experimental apparatus that can load an order of magnitude more atoms than usual, to yield the extremely high optical depths needed for high-efficiency quantum memories.

arXiv:1802.05396•Physical Review Applied•Oct 12, 2018•23 citations

Loading Dynamics of Cold Atoms into a Hollow-Core Photonic Crystal Fiber

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Cold atoms trapped and guided in hollow-core photonic crystal fibers provide a scalable diffraction-free setting for atom–light interactions for quantum technologies. However, due to the mismatch of the depth and spatial extension of the trapping potential from free space to the fiber, the number of cold atoms in the fiber is mainly determined by the loading process from free space to waveguide confinement. Here, we provide a numerical study of the loading dynamics of cold atoms into a hollow-core photonic crystal fiber. We use the Monte Carlo method to simulate the trajectories of an ensemble of cold atoms from free space trapping potential to optical potential inside a hollow-core fiber and calculate the temperature, loading efficiency, and geometry of the ensemble. We also study the noise sources that cause heating and a loss of atoms during the process. Our result could be used to design and optimize the loading process of cold atoms into a hollow-core fiber for cold atom experiments.

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Loading and spatially resolved characterization of a cold atomic ensemble inside a hollow-core fiber

Thorsten Peters, Леонід Петрович Яценко, Thomas Halfmann

We present a thorough experimental investigation of the loading process of laser-cooled atoms from a magneto-optical trap into an optical dipole trap located inside a hollow-core photonic bandgap fiber, followed by propagation of the atoms therein. This, e.g., serves to identify limits to the loading efficiency and thus optical depth which is a key parameter for applications in quantum information technology. Although only limited access in 1D is available to probe atoms inside such a fiber, we demonstrate that a detailed spatially resolved characterization of the loading and trapping process along the fiber axis is possible by appropriate modification of probing techniques combined with theoretical analysis. Specifically, we demonstrate the loading of up to $2.1\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms with a transfer efficiency of $2.1%$ during the course of 50 ms and a peak loading rate of $4.7\ifmmode\times\else\texttimes\fi{}{10}^{3}$ atoms ${\mathrm{ms}}^{\ensuremath{-}1}$ resulting in a peak atomic number density on the order of ${10}^{12}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. Furthermore, we determine the evolution of the spatial density (profile) and ensemble temperature as it approaches its steady-state value of $T=1400\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{K}$, as well as loss rates, axial velocity and acceleration. The spatial resolution along the fiber axis reaches a few millimeters, which is much smaller than the typical fiber length in experiments. We compare our results to other fiber-based as well as free-space optical dipole traps and discuss the potential for further improvements.

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Atom guiding in free-space light beams and photonic crystal fibres

J. Livesey

In this thesis I describe experimental work and present data on the guiding of \nRubidium atoms along free-space propagating light beams as well as within hollow \ncore glass fibres, namely photonic crystal fibres. I describe experiments, laser systems \nand vacuum trap assemblies designed to facilitate this guiding. \nThese experiments are intended to aid progression within the field of cold \natom guidance wherein narrow diameter, long distance hollow-fibre guides are a \ncurrent goal. Realisation of these guides could lead to promising applications such as \natom interferometers and spatially accurate, multi-source, atom depositors. \nHerein, guided fluxes are observed in free-space guiding experiments for \ndistances up to 50mm and up to 10GHz red-detuning from resonance. Additionally \nhollow-core, Kagome structured, quasi- and true-photonic crystal fibres are \ncharacterised. Finally a number of detailed fibre-guiding magneto-optic traps are \ndeveloped. \nBoth cold atomic-beams and cold atomic clouds are reliably positioned above \nfibre entrance facets in conjunction with a guiding laser beam coupled into the fibre \ncore. \nIssues regarding optical flux detection outwith fibre confinement appear to \nhave hindered observation of guided atoms. A far more sensitive detection system has \nbeen developed for use in current, ongoing fibre-guide experiments.

•Jan 1, 2007•0 citations

Integrating cold caesium atoms into optical waveguides

Elisa Da Ros

This project focuses on a novel experimental method for interfacing cold atoms with optical waveguides. This relies on the introduction of cold atoms into microscopic laser-drilled holes that are perpendicular to the propagation axis of the waveguide. Direct interfacing of cold atoms with the guided mode of a waveguide is an attractive mechanism by which to create atom-photon interfaces, as the small mode area increases the interaction rate. Unlike many previous approaches, this technique can be applied in almost any existing waveguide system, including chip-based waveguide arrays and other complex environments. It therefore has great promise as a way of creating hybrid atom-photon quantum devices. Using this method, we demonstrate coupling between cold atoms and the light propagating in the core of an untapered single-mode optical fibre. This was achieved by laser-drilling a cylindrical, transverse hole (30 μm diameter) through the core of the fibre. Ensembles of cold caesium atoms can be tightly confined through an optical dipole trap within the microscopic void. Probe light, resonant with the Cs D2 line, is then coupled into the fibre. By measuring the transmitted optical power through the interface, it was determined that up to 87% of the probe power could be absorbed by the atoms. The corresponding optical depth per unit length of the atom cloud is over 700 cm^(-1), higher than any value reported to date for a comparable system. This will be a key parameter for the miniaturisation of atom-optical systems as well as for enhancing spatial resolution in sensing applications. The dependence of this absorption on several experimental parameters was also characterised and found to be in line with theoretical expectations. The atomic transition is not noticeably broadened by the presence of the fibre. We have also carried out numerical simulations of light transmission across wave-guide junctions of this type, proving that tailored hole geometries can enable enhanced optical transmission. The achievable degree of improvement is such that it is conceivable to place the void within an optical resonator, for example using laser-written Bragg gratings, and to achieve the strong coupling between the atoms and the guided light. Altogether this work demonstrates the potential of this technique to interface atoms with tightly confined light, allowing for integration in otherwise purely photonic circuits. In such environment the interaction between the atomic ensemble and the light can act as a node for the storage and processing of quantum information.

•Dec 31, 2020•0 citations

Atom guiding along "non-diffracting" light beams

Jochen Arlt, C. A. McQueen, Kishan Dholakia

Summary form only given. Recent advances in cold atom physics have seen the emergence of the area of atom guiding along hollow core optical fibres and also along light beams. Both employ the optical dipole force which for suitably tuned light can restrict the atoms to the dark hollow region of the fibre or the light beam. In this work, we discuss and analyse a novel scheme of channelling cold atoms into a high-order Bessel beam (via a high-order Laguerre-Gaussian beam) and demonstrate an efficient method of producing such beams.

Quantum Electronics and Laser Science Conference•Jan 20, 2003•0 citations
We have developed an atom-guiding technique that loads 3×1063\times 10^63×106 cold rubidium atoms into hollow-core optical fibre, an order-of-magnitude larger than previously reported results. This achievement was guided by a physically realistic simulation that led to an experimental loading efficiency of 3%3\%3%, giving a peak optical depth of over 600600600. The loading efficiency was limited only by the geometric overlap of the atom cloud an an optical guide beam, and we have identified techniques that would allows us to exceed this limit. We also present a fast and minimally destructive probing technique that enables us to follow the dynamics of the cold atom cloud as it falls into the fibre - this strengthens the confidence in our detailed model, and enables adjustment of the experiment into an optimal state. We are able to observe the effect of light-assisted cold atom collisions as well as background gas collisions in the fibre. The combination of these observations and physical understanding from the simulation allows us to estimate the ultimate limits to loading cold atoms into hollow-core fibres.
Hollow-core optical fibers loaded with cold atoms show great promise as platforms for quantum information processing and highly nonlinear optics, but their limitations have remained poorly understood. Using detailed Monte Carlo simulation, the authors model the loading dynamics and predict the sensitivity of the system to various experimental parameters. Thus guided, they develop an experimental apparatus that can load an order of magnitude more atoms than usual, to yield the extremely high optical depths needed for high-efficiency quantum memories.
Cold atoms trapped and guided in hollow-core photonic crystal fibers provide a scalable diffraction-free setting for atom–light interactions for quantum technologies. However, due to the mismatch of the depth and spatial extension of the trapping potential from free space to the fiber, the number of cold atoms in the fiber is mainly determined by the loading process from free space to waveguide confinement. Here, we provide a numerical study of the loading dynamics of cold atoms into a hollow-core photonic crystal fiber. We use the Monte Carlo method to simulate the trajectories of an ensemble of cold atoms from free space trapping potential to optical potential inside a hollow-core fiber and calculate the temperature, loading efficiency, and geometry of the ensemble. We also study the noise sources that cause heating and a loss of atoms during the process. Our result could be used to design and optimize the loading process of cold atoms into a hollow-core fiber for cold atom experiments.
We present a thorough experimental investigation of the loading process of laser-cooled atoms from a magneto-optical trap into an optical dipole trap located inside a hollow-core photonic bandgap fiber, followed by propagation of the atoms therein. This, e.g., serves to identify limits to the loading efficiency and thus optical depth which is a key parameter for applications in quantum information technology. Although only limited access in 1D is available to probe atoms inside such a fiber, we demonstrate that a detailed spatially resolved characterization of the loading and trapping process along the fiber axis is possible by appropriate modification of probing techniques combined with theoretical analysis. Specifically, we demonstrate the loading of up to $2.1\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms with a transfer efficiency of 2.12.1%2.1 during the course of 50 ms and a peak loading rate of $4.7\ifmmode\times\else\texttimes\fi{}{10}^{3}$ atoms ${\mathrm{ms}}^{\ensuremath{-}1}$ resulting in a peak atomic number density on the order of ${10}^{12}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. Furthermore, we determine the evolution of the spatial density (profile) and ensemble temperature as it approaches its steady-state value of $T=1400\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{K}$, as well as loss rates, axial velocity and acceleration. The spatial resolution along the fiber axis reaches a few millimeters, which is much smaller than the typical fiber length in experiments. We compare our results to other fiber-based as well as free-space optical dipole traps and discuss the potential for further improvements.
In this thesis I describe experimental work and present data on the guiding of \nRubidium atoms along free-space propagating light beams as well as within hollow \ncore glass fibres, namely photonic crystal fibres. I describe experiments, laser systems \nand vacuum trap assemblies designed to facilitate this guiding. \nThese experiments are intended to aid progression within the field of cold \natom guidance wherein narrow diameter, long distance hollow-fibre guides are a \ncurrent goal. Realisation of these guides could lead to promising applications such as \natom interferometers and spatially accurate, multi-source, atom depositors. \nHerein, guided fluxes are observed in free-space guiding experiments for \ndistances up to 50mm and up to 10GHz red-detuning from resonance. Additionally \nhollow-core, Kagome structured, quasi- and true-photonic crystal fibres are \ncharacterised. Finally a number of detailed fibre-guiding magneto-optic traps are \ndeveloped. \nBoth cold atomic-beams and cold atomic clouds are reliably positioned above \nfibre entrance facets in conjunction with a guiding laser beam coupled into the fibre \ncore. \nIssues regarding optical flux detection outwith fibre confinement appear to \nhave hindered observation of guided atoms. A far more sensitive detection system has \nbeen developed for use in current, ongoing fibre-guide experiments.
This project focuses on a novel experimental method for interfacing cold atoms with optical waveguides. This relies on the introduction of cold atoms into microscopic laser-drilled holes that are perpendicular to the propagation axis of the waveguide. Direct interfacing of cold atoms with the guided mode of a waveguide is an attractive mechanism by which to create atom-photon interfaces, as the small mode area increases the interaction rate. Unlike many previous approaches, this technique can be applied in almost any existing waveguide system, including chip-based waveguide arrays and other complex environments. It therefore has great promise as a way of creating hybrid atom-photon quantum devices. Using this method, we demonstrate coupling between cold atoms and the light propagating in the core of an untapered single-mode optical fibre. This was achieved by laser-drilling a cylindrical, transverse hole (30 μm diameter) through the core of the fibre. Ensembles of cold caesium atoms can be tightly confined through an optical dipole trap within the microscopic void. Probe light, resonant with the Cs D2 line, is then coupled into the fibre. By measuring the transmitted optical power through the interface, it was determined that up to 87% of the probe power could be absorbed by the atoms. The corresponding optical depth per unit length of the atom cloud is over 700 cm^(-1), higher than any value reported to date for a comparable system. This will be a key parameter for the miniaturisation of atom-optical systems as well as for enhancing spatial resolution in sensing applications. The dependence of this absorption on several experimental parameters was also characterised and found to be in line with theoretical expectations. The atomic transition is not noticeably broadened by the presence of the fibre. We have also carried out numerical simulations of light transmission across wave-guide junctions of this type, proving that tailored hole geometries can enable enhanced optical transmission. The achievable degree of improvement is such that it is conceivable to place the void within an optical resonator, for example using laser-written Bragg gratings, and to achieve the strong coupling between the atoms and the guided light. Altogether this work demonstrates the potential of this technique to interface atoms with tightly confined light, allowing for integration in otherwise purely photonic circuits. In such environment the interaction between the atomic ensemble and the light can act as a node for the storage and processing of quantum information.
Summary form only given. Recent advances in cold atom physics have seen the emergence of the area of atom guiding along hollow core optical fibres and also along light beams. Both employ the optical dipole force which for suitably tuned light can restrict the atoms to the dark hollow region of the fibre or the light beam. In this work, we discuss and analyse a novel scheme of channelling cold atoms into a high-order Bessel beam (via a high-order Laguerre-Gaussian beam) and demonstrate an efficient method of producing such beams.