Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Raman gain and lasing from cold potassium atoms in a ring cavity

Graeme Harvie

Published Jul 1, 2020• 0 citations
OpenAlex

Abstract

This thesis describes an experiment with a cloud of magneto-optically trapped Potassium-39 spatially overlapped with the modes of a high-finesse ring cavity. Optical gain was observed with the system in steady state, without any beams additional to the normal cooling and repump beams in a potassium-39 magneto-optical trap. This was found to operate on a Raman gain mechanism between atomic hyperfine ground states, which has not been seen under similar conditions with other atomic species. Lasing into the cavity modes was then studied, with a particular focus on aspects specific to the ring cavity geometry. This showed a directional bistability and non-reciprocity. The bistability can be described by existing theory, but the mechanism of the non-reciprocity is unknown, despite a detailed investigation. The second order coherence time of the system was explored below threshold, and demonstrates a strong dependence on gain, which may have applications in the detection of extremely small gains.

Related papers

Cold atom ring laser

Balázs Megyeri

This thesis will describe a cold atom ring laser that uses a cloud of magneto-optically trapped potassium atoms as a gain medium and a ring cavity for feedback. Some upgrades to the experiment were necessary, which include a new imaging axis in the vacuum system, a new atom source, alignment of some new optics and detectors to measure the powers and transverse intensity profiles of both counterpropagating cavity modes, and a new tapered amplifier for the magneto-optical trapping beams. The lasing threshold, gain mechanism, intensity correlations, and lasing into the two counterpropagating cavity modes were investigated. The results showed several transverse patterns at the lasing outputs, a threshold as a function of atom number, Mollow gain, a at second-order coherence above threshold, clearly distinguishable from that of fluorescence, nonreciprocity of the TEM\\(_{00}\\) transverse mode as a function of cavity length, and anticorrelated counterpropagating modes.

•Jul 11, 2019•0 citations

Directional Bistability and Nonreciprocal Lasing with Cold Atoms in a Ring Cavity

Balázs Megyeri, Graeme Harvie, Andreas Lampis +1 more

We demonstrate lasing into counterpropagating modes of a ring cavity using a gas of cold atoms as a gain medium. The laser operates under the usual conditions of magneto-optical trapping with no additional fields. We characterize the threshold behavior of the laser and measure the second-order optical coherence. The laser emission exhibits directional bistability, switching randomly between clockwise and counterclockwise modes, and a tunable nonreciprocity is observed as the atoms are displaced along the cavity axis.

arXiv:1810.03147•Physical Review Letters•Oct 19, 2018•25 citations

Collective strong coupling of cold potassium atoms in an optical ring cavity

Robert Culver

This thesis describes an experiment which studies a cloud of magneto-optically trapped potassium-39 atoms inside an optical ring cavity. The potassium atoms are firstly cooled in a two-dimensional magneto-optical trap (MOT) and are then transferred into a three dimensional MOT which overlaps with the cavity mode. In this thesis, the optimisation of the MOT systems and the characterisation and construction of the optical ring cavity are discussed. After exploring these two systems independently, the two systems are then coupled together to provide an atom-cavity system, which exhibits collective strong coupling. The system is shown to exhibit normal-mode splitting, with a collective Rabi splitting of G = 2π (6.25±0.50)MHz, corresponding to (4.7±0.6) x 10³ atoms in the cavity. Whilst collective strong coupling has been achieved before in other experiments, we believe this is the first experiment to achieve this with potassium. \n \nThe next goal in the experiment is to control the group refractive index of the atoms inside the cavity. The modification of the group index using electromagnetically-induced transparency (EIT) on hot atoms inside a vapour cell has already been previously demonstrated by this experiment; and using the same laser system we aim to demonstrate EIT on the cold intra-cavity atoms as well. Gain mechanisms could also be used to create a ring laser with a controllable group index. These techniques could lead to a range of applications such as enhanced-sensitivity laser ring gyroscopes and active optical clocks. \n \n

•Jul 1, 2017•1 citation

Magneto optical trapping of potassium-39 in a ring cavity

K Pahwa

This thesis focuses on the construction and development of an experiment to study cold potassium atoms in an optical ring cavity. Firstly we load a potassium-39 magneto optical trap (MOT) inside the ring cavity. To achieve this a laser system, rectangular magnetic coils system and vacuum system are designed and constructed. To stabilise the laser system, a detailed study of various potassium spectroscopy techniques is undertaken and the reference laser is suitably locked to the magnetically induced spectroscopy. We load an ensemble of 10\\(^5\\) potassium atoms inside the ring cavity mode and study their collective strong coupling with the cavity field. In the collective strong coupling regime, the photons are coherently exchanged between the atomic ensemble and cavity field. This rate of exchange is determined by the singlephoton Rabi frequency `2\\(g\\)' which must be larger than the cavity field decay rate `2\\(k\\)' and atomic spontaneous emission rate `2\\(ᵧ\\)'. As a result of this coupling, the peak in the cavity transmission signal undergoes a splitting known as `vacuum Rabi splitting' (or `normal mode splitting'). The vacuum Rabi splitting has been realised and measured to be ~ 2\\(π\\). 18 MHz in our system.

•Dec 1, 2014•1 citation

In situ Raman gain between hyperfine ground states in a potassium magneto-optical trap

Graeme Harvie, Adam Butcher, J. Goldwin

We study optical gain in a gas of cold $^{39}\mathrm{K}$ atoms. The gain is observed during operation of a conventional magneto-optical trap without the need for additional fields. Measurements of transmission spectra from a weak probe show that the gain is due to stimulated Raman scattering between hyperfine ground states. The experimental results are reproduced by a simplified six-level model, which also helps explain why such gain is not observed in similar experiments with rubidium or cesium.

arXiv:1906.05756•Physical Review A•Sep 9, 2019•4 citations

Collective strong coupling of cold potassium atoms in a ring cavity

Robert Culver, Andreas Lampis, Balázs Megyeri +5 more

We present experiments on ensemble cavity quantum electrodynamics with cold potassium atoms in a high-finesse ring cavity.Potassium-39 atoms are cooled in a two-dimensional magneto-optical trap and transferred to a three-dimensional trap which intersects the cavity mode.The apparatus is described in detail and the first observations of strong coupling with potassium atoms are presented.Collective strong coupling of atoms and light is demonstrated via the splitting of the cavity transmission spectrum and the avoided crossing of the normal modes.

arXiv:1608.06725•New Journal of Physics•Nov 24, 2016•23 citations
This thesis describes an experiment with a cloud of magneto-optically trapped Potassium-39 spatially overlapped with the modes of a high-finesse ring cavity. Optical gain was observed with the system in steady state, without any beams additional to the normal cooling and repump beams in a potassium-39 magneto-optical trap. This was found to operate on a Raman gain mechanism between atomic hyperfine ground states, which has not been seen under similar conditions with other atomic species. Lasing into the cavity modes was then studied, with a particular focus on aspects specific to the ring cavity geometry. This showed a directional bistability and non-reciprocity. The bistability can be described by existing theory, but the mechanism of the non-reciprocity is unknown, despite a detailed investigation. The second order coherence time of the system was explored below threshold, and demonstrates a strong dependence on gain, which may have applications in the detection of extremely small gains.
This thesis will describe a cold atom ring laser that uses a cloud of magneto-optically trapped potassium atoms as a gain medium and a ring cavity for feedback. Some upgrades to the experiment were necessary, which include a new imaging axis in the vacuum system, a new atom source, alignment of some new optics and detectors to measure the powers and transverse intensity profiles of both counterpropagating cavity modes, and a new tapered amplifier for the magneto-optical trapping beams. The lasing threshold, gain mechanism, intensity correlations, and lasing into the two counterpropagating cavity modes were investigated. The results showed several transverse patterns at the lasing outputs, a threshold as a function of atom number, Mollow gain, a at second-order coherence above threshold, clearly distinguishable from that of fluorescence, nonreciprocity of the TEM\\(_{00}\\) transverse mode as a function of cavity length, and anticorrelated counterpropagating modes.
We demonstrate lasing into counterpropagating modes of a ring cavity using a gas of cold atoms as a gain medium. The laser operates under the usual conditions of magneto-optical trapping with no additional fields. We characterize the threshold behavior of the laser and measure the second-order optical coherence. The laser emission exhibits directional bistability, switching randomly between clockwise and counterclockwise modes, and a tunable nonreciprocity is observed as the atoms are displaced along the cavity axis.
This thesis describes an experiment which studies a cloud of magneto-optically trapped potassium-39 atoms inside an optical ring cavity. The potassium atoms are firstly cooled in a two-dimensional magneto-optical trap (MOT) and are then transferred into a three dimensional MOT which overlaps with the cavity mode. In this thesis, the optimisation of the MOT systems and the characterisation and construction of the optical ring cavity are discussed. After exploring these two systems independently, the two systems are then coupled together to provide an atom-cavity system, which exhibits collective strong coupling. The system is shown to exhibit normal-mode splitting, with a collective Rabi splitting of G = 2π (6.25±0.50)MHz, corresponding to (4.7±0.6) x 10³ atoms in the cavity. Whilst collective strong coupling has been achieved before in other experiments, we believe this is the first experiment to achieve this with potassium. \n \nThe next goal in the experiment is to control the group refractive index of the atoms inside the cavity. The modification of the group index using electromagnetically-induced transparency (EIT) on hot atoms inside a vapour cell has already been previously demonstrated by this experiment; and using the same laser system we aim to demonstrate EIT on the cold intra-cavity atoms as well. Gain mechanisms could also be used to create a ring laser with a controllable group index. These techniques could lead to a range of applications such as enhanced-sensitivity laser ring gyroscopes and active optical clocks. \n \n
This thesis focuses on the construction and development of an experiment to study cold potassium atoms in an optical ring cavity. Firstly we load a potassium-39 magneto optical trap (MOT) inside the ring cavity. To achieve this a laser system, rectangular magnetic coils system and vacuum system are designed and constructed. To stabilise the laser system, a detailed study of various potassium spectroscopy techniques is undertaken and the reference laser is suitably locked to the magnetically induced spectroscopy. We load an ensemble of 10\\(^5\\) potassium atoms inside the ring cavity mode and study their collective strong coupling with the cavity field. In the collective strong coupling regime, the photons are coherently exchanged between the atomic ensemble and cavity field. This rate of exchange is determined by the singlephoton Rabi frequency `2\\(g\\)' which must be larger than the cavity field decay rate `2\\(k\\)' and atomic spontaneous emission rate `2\\(ᵧ\\)'. As a result of this coupling, the peak in the cavity transmission signal undergoes a splitting known as `vacuum Rabi splitting' (or `normal mode splitting'). The vacuum Rabi splitting has been realised and measured to be ~ 2\\(π\\). 18 MHz in our system.
We study optical gain in a gas of cold 39K^{39}\mathrm{K}39K atoms. The gain is observed during operation of a conventional magneto-optical trap without the need for additional fields. Measurements of transmission spectra from a weak probe show that the gain is due to stimulated Raman scattering between hyperfine ground states. The experimental results are reproduced by a simplified six-level model, which also helps explain why such gain is not observed in similar experiments with rubidium or cesium.
We present experiments on ensemble cavity quantum electrodynamics with cold potassium atoms in a high-finesse ring cavity.Potassium-39 atoms are cooled in a two-dimensional magneto-optical trap and transferred to a three-dimensional trap which intersects the cavity mode.The apparatus is described in detail and the first observations of strong coupling with potassium atoms are presented.Collective strong coupling of atoms and light is demonstrated via the splitting of the cavity transmission spectrum and the avoided crossing of the normal modes.