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

Optics Continuum

Gain, amplification, and lasing in a driven atom-cavity system

Arun Bahuleyan, V. R. Thakar, V. I. Gokul, S. P. Dinesh, B. Prasanna Venkatesh, S. A. Rangwala

Published Mar 25, 2025• 2 citations
Publisher

Abstract

Cold atoms coupled to an optical cavity provide an ideal platform for creating lasers without conventional population inversion. Such lasers can generate very high spectral purity, and the output can be precisely controlled by varying the atom-drive or atom-cavity parameters. In this letter, we report experimental observation of gain, amplification, and self-lasing within a continuously operated 85 Rb magneto-optic trap (MOT), in the collective strong coupling regime of the atom-cavity system. The presence of MOT cooling lasers significantly alters the transmission properties of the cavity, and gain is observed in one of the vacuum Rabi peaks. The system makes a transition from an amplifying medium to a self-sustained laser as the MOT parameters are tuned. The underlying lasing mechanism is shown to be Mollow gain in the driven atomic ensemble, and is confirmed through the free-space absorption spectroscopy of the MOT. The free space gain required for the lasing action is significantly smaller in our system as compared to the cases where there is no collective strong coupling.

DOI
10.1364/optcon.540845

Related papers

Lasing by driven atoms-cavity system in collective strong coupling regime

Rahul Sawant, S. A. Rangwala

The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.

arXiv:1705.08075•Scientific Reports•Sep 6, 2017•16 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

A superradiant two-level laser with intrinsic light force generated gain

Anna A. Bychek, Helmut Ritsch

Abstract The implementation of a superradiant laser as an active frequency standard is predicted to provide better short-term stability and robustness to thermal and mechanical fluctuations when compared to standard passive optical clocks. However, despite significant recent progress, the experimental realization of continuous wave superradiant lasing still remains an open challenge as it requires continuous loading, cooling, and pumping of active atoms within an optical resonator. Here we propose a new scenario for creating continuous gain by using optical forces acting on the states of a two-level atom via bichromatic coherent pumping of a cold atomic gas trapped inside a single-mode cavity. Analogous to atomic maser setups, tailored state-dependent forces are used to gather and concentrate excited-state atoms in regions of strong atom-cavity coupling while ground-state atoms are repelled. To facilitate numerical simulations of a sufficiently large atomic ensemble, we rely on a second-order cumulant expansion and describe the atomic motion in a semi-classical point-particle approximation subject to position-dependent light shifts which induce optical gradient forces along the cavity axis. We study minimal conditions on pump laser intensities and detunings required for collective superradiant emission. Balancing Doppler cooling and gain-induced heating we identify a parameter regime of a continuous narrow-band laser operation close to the bare atomic frequency.

arXiv:2304.13190•New Journal of Physics•Oct 26, 2023•2 citations

Raman Lasing with a Cold Atom Gain Medium in a High-Finesse Optical Cavity

Geert Vrijsen, Onur Hosten, Jongmin Lee +2 more

We demonstrate a Raman laser using cold (87)Rb atoms as the gain medium in a high-finesse optical cavity. We observe robust continuous wave lasing in the atypical regime where single atoms can considerably affect the cavity field. Consequently, we discover unusual lasing threshold behavior in the system causing jumps in lasing power, and propose a model to explain the effect. We also measure the intermode laser linewidth, and observe values as low as 80 Hz. The tunable gain properties of this laser suggest multiple directions for future research.

Physical Review Letters•Aug 4, 2011•36 citations

Superradiant Cooling, Trapping and Lasing of Dipole-Interacting Clock Atoms

Christoph Hotter

A cold atomic gas with an inverted population on a transition coupled to a field mode of an optical resonator constitutes a generic model of a laser. For quasi-continuous operation, external pumping, trapping and cooling of the atoms is required to confine them in order to achieve enough gain inside the resonator. As inverted atoms are high-field seekers in blue detuned light fields, tuning the cavity mode to the blue side of the atomic gain transition allows for combining lasing with stimulated cavity cooling and dipole trapping of the atoms at the antinodes of the laser field. We study such a configuration using a semiclassical description of particle motion along the cavity axis. In extension of earlier work we include free space atomic and cavity decay as well as atomic dipole-dipole interactions and their corresponding forces. We show that for a proper choice of parameters even in the bad cavity limit the atoms can create a sufficiently strong field inside the resonator such that they are trapped and cooled via the superradiant lasing action with less than one photon on average inside the cavity.

•Jan 1, 2018•18 citations

Superradiant cooling, trapping, and lasing of dipole-interacting clock atoms

Christoph Hotter, David Plankensteiner, Laurin Ostermann +1 more

A cold atomic gas with an inverted population on a transition coupled to a field mode of an optical resonator constitutes a generic model of a laser. For quasi-continuous operation, external pumping, trapping and cooling of the atoms is required to confine them in order to achieve enough gain inside the resonator. As inverted atoms are high-field seekers in blue detuned light fields, tuning the cavity mode to the blue side of the atomic gain transition allows for combining lasing with stimulated cavity cooling and dipole trapping of the atoms at the antinodes of the laser field. We study such a configuration using a semiclassical description of particle motion along the cavity axis. In extension of earlier work we include free space atomic and cavity decay as well as atomic dipole-dipole interactions and their corresponding forces. We show that for a proper choice of parameters even in the bad cavity limit the atoms can create a sufficiently strong field inside the resonator such that they are trapped and cooled via the superradiant lasing action with less than one photon on average inside the cavity.

arXiv:1906.01945•Optics Express•Oct 14, 2019•22 citations
Cold atoms coupled to an optical cavity provide an ideal platform for creating lasers without conventional population inversion. Such lasers can generate very high spectral purity, and the output can be precisely controlled by varying the atom-drive or atom-cavity parameters. In this letter, we report experimental observation of gain, amplification, and self-lasing within a continuously operated 85 Rb magneto-optic trap (MOT), in the collective strong coupling regime of the atom-cavity system. The presence of MOT cooling lasers significantly alters the transmission properties of the cavity, and gain is observed in one of the vacuum Rabi peaks. The system makes a transition from an amplifying medium to a self-sustained laser as the MOT parameters are tuned. The underlying lasing mechanism is shown to be Mollow gain in the driven atomic ensemble, and is confirmed through the free-space absorption spectroscopy of the MOT. The free space gain required for the lasing action is significantly smaller in our system as compared to the cases where there is no collective strong coupling.
The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.
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
Abstract The implementation of a superradiant laser as an active frequency standard is predicted to provide better short-term stability and robustness to thermal and mechanical fluctuations when compared to standard passive optical clocks. However, despite significant recent progress, the experimental realization of continuous wave superradiant lasing still remains an open challenge as it requires continuous loading, cooling, and pumping of active atoms within an optical resonator. Here we propose a new scenario for creating continuous gain by using optical forces acting on the states of a two-level atom via bichromatic coherent pumping of a cold atomic gas trapped inside a single-mode cavity. Analogous to atomic maser setups, tailored state-dependent forces are used to gather and concentrate excited-state atoms in regions of strong atom-cavity coupling while ground-state atoms are repelled. To facilitate numerical simulations of a sufficiently large atomic ensemble, we rely on a second-order cumulant expansion and describe the atomic motion in a semi-classical point-particle approximation subject to position-dependent light shifts which induce optical gradient forces along the cavity axis. We study minimal conditions on pump laser intensities and detunings required for collective superradiant emission. Balancing Doppler cooling and gain-induced heating we identify a parameter regime of a continuous narrow-band laser operation close to the bare atomic frequency.
We demonstrate a Raman laser using cold (87)Rb atoms as the gain medium in a high-finesse optical cavity. We observe robust continuous wave lasing in the atypical regime where single atoms can considerably affect the cavity field. Consequently, we discover unusual lasing threshold behavior in the system causing jumps in lasing power, and propose a model to explain the effect. We also measure the intermode laser linewidth, and observe values as low as 80 Hz. The tunable gain properties of this laser suggest multiple directions for future research.
A cold atomic gas with an inverted population on a transition coupled to a field mode of an optical resonator constitutes a generic model of a laser. For quasi-continuous operation, external pumping, trapping and cooling of the atoms is required to confine them in order to achieve enough gain inside the resonator. As inverted atoms are high-field seekers in blue detuned light fields, tuning the cavity mode to the blue side of the atomic gain transition allows for combining lasing with stimulated cavity cooling and dipole trapping of the atoms at the antinodes of the laser field. We study such a configuration using a semiclassical description of particle motion along the cavity axis. In extension of earlier work we include free space atomic and cavity decay as well as atomic dipole-dipole interactions and their corresponding forces. We show that for a proper choice of parameters even in the bad cavity limit the atoms can create a sufficiently strong field inside the resonator such that they are trapped and cooled via the superradiant lasing action with less than one photon on average inside the cavity.
A cold atomic gas with an inverted population on a transition coupled to a field mode of an optical resonator constitutes a generic model of a laser. For quasi-continuous operation, external pumping, trapping and cooling of the atoms is required to confine them in order to achieve enough gain inside the resonator. As inverted atoms are high-field seekers in blue detuned light fields, tuning the cavity mode to the blue side of the atomic gain transition allows for combining lasing with stimulated cavity cooling and dipole trapping of the atoms at the antinodes of the laser field. We study such a configuration using a semiclassical description of particle motion along the cavity axis. In extension of earlier work we include free space atomic and cavity decay as well as atomic dipole-dipole interactions and their corresponding forces. We show that for a proper choice of parameters even in the bad cavity limit the atoms can create a sufficiently strong field inside the resonator such that they are trapped and cooled via the superradiant lasing action with less than one photon on average inside the cavity.