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

International Conference on Transparent Optical Networks

Coherent Photon Statistics in a Superradiant Laser

Kyungwon An

Published Jul 14, 2024• 0 citations
Publisher

Abstract

It has been widely accepted that the conventional lasing threshold, occurring around unity intracavity photon number, can be eliminated by making the so-called $\beta$ parameter approach unity. Recently, it has been shown that the photon statistics become incoherent when the intracavity mean photon number is decreased below unity even for $\beta \approx 1$. Here, we report systematic measurement of the photon statistics in a superradiant laser as a function of the intracavity photon number. Our superradiant laser was based on the single-atom superradiance driven by twolevel atoms in a quantum superposition state traversing a high-Q cavity one by one. The lasing did not exhibit the conventional threshold and the photon statistics remained near coherent even well below unity photon number. Moreover, the coherence got better as the excited-state population in the initial superposition state was made smaller.

DOI
10.1109/icton62926.2024.10647959

Related papers

Thresholdless coherence in a superradiant laser

Seung-Hoon Oh, Jinuk Kim, Junseo Ha +2 more

Lasing threshold in the conventional lasers is the minimum input power required to initiate laser oscillation. It has been widely accepted that the conventional laser threshold occurring around a unity intracavity photon number can be eliminated in the input-output curve by making the so-called β parameter approach unity. The recent experiments, however, have revealed that even in this case the photon statistics still undergo a transition from coherent to thermal statistics when the intracavity mean photon number is decreased below unity. Since the coherent output is only available above the diminished threshold, the long-sought promise of thresholdless lasers to produce always coherent light has become questionable. Here, we present an always-coherent thresholdless laser based on superradiance by two-level atoms in a quantum superposition state with the same phase traversing a high-Q cavity. Superradiant lasing was observed without the conventional lasing threshold around the unity photon number and the photon statistics remained near coherent even below it. The coherence was improved by reducing the coupling constant as well as the excited-state amplitude in the superposition state. Our results pave a way toward always-coherent thresholdless lasers with more practical media such as quantum dots, nitrogen-vacancy centers and doped ions in crystals.

Light Science & Applications•Sep 5, 2024•6 citations

Subnatural Linewidth Superradiant Lasing with Cold Sr 88 Atoms

Sofus L. Kristensen, Eliot A. Bohr, Julian Robinson-Tait +3 more

Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold ^{88}Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide ^{3}P_{1}→^{1}S_{0} intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth.

Physical Review Letters•May 31, 2023•23 citations

Sub-Natural Linewidth Superradiant Lasing with Cold $^{88}$Sr Atoms

Sofus L. Kristensen, Eliot A. Bohr, Julian Robinson-Tait +3 more

Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold $^{88}$Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide $^3P_1$ $\rightarrow$ $^1S_0$ intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth

arXiv:2302.08977•Feb 17, 2023•0 citations

Photon statistics of a single atom laser

Bobby D. Jones, Shohini Ghose, James Clemens +2 more

We consider a laser model consisting of a single four-level or three-level atom, an optical cavity, and an incoherent pump. Results for photon statistics for varying pump levels are obtained using a quantum trajectory algorithm. In particular, we calculate the mean photon number, Fano factor (which is the variance over the mean). We examine that the behavior of the single-atom device as \ensuremath{\beta}, the fraction of spontaneous emission into the lasing mode, is varied. Typical values considered for \ensuremath{\beta} are $0.01<\ensuremath{\beta}<1.0.$ We find that for large enough \ensuremath{\beta}, lasing action, with properties similar to those predicted by semiclassical theories that factorize atom-field correlations and use a small-noise approximation, can occur. Squeezing can occur as \ensuremath{\beta} is increased. There is no evidence of a sharp phase transition from weakly excited thermal light to coherent light at a particular pump power. This is consistent with work on many-atom lasers with \ensuremath{\beta} values in the range considered here. As \ensuremath{\beta} is increased, the output goes from quasithermal light to coherent and finally to squeezed light, progressing into a fully quantum-mechanical regime. We also consider the effects of cavity damping and spontaneous emission rates on these results.

Physical Review A•Oct 1, 1999•57 citations

Photon statistics and emission spectrum of single-atom superradiance

Kyungwon

We have investigated the photon statistics as well as the spectrum of the output emission from an atom-cavity system made of a small number of phase-correlated atoms undergoing superradiant lasing in a high-Q cavity.

International Conference on Transparent Optical Networks•Jul 6, 2025•0 citations

Quantum statistical properties of one-atom lasers

T. B. Karlovich, S. Ya. Kilin

Properties of a laser formed by a high-Q cavity and a single incoherently excited atom are studied on the basis of analytical solutions obtained for the quasi-probability P -function. Expressions for the boundaries separating various operating regimes of a one-atom laser (below threshold, above threshold, and self-quenching) are found. It is shown that lasing without inversion and lasing with the decay rate of the excited state exceeding the pump intensity are possible in the system. The degree of coherence of laser radiation is studied.

Optics and Spectroscopy•Sep 1, 2001•26 citations
It has been widely accepted that the conventional lasing threshold, occurring around unity intracavity photon number, can be eliminated by making the so-called β\betaβ parameter approach unity. Recently, it has been shown that the photon statistics become incoherent when the intracavity mean photon number is decreased below unity even for β≈1\beta \approx 1β≈1. Here, we report systematic measurement of the photon statistics in a superradiant laser as a function of the intracavity photon number. Our superradiant laser was based on the single-atom superradiance driven by twolevel atoms in a quantum superposition state traversing a high-Q cavity one by one. The lasing did not exhibit the conventional threshold and the photon statistics remained near coherent even well below unity photon number. Moreover, the coherence got better as the excited-state population in the initial superposition state was made smaller.
Lasing threshold in the conventional lasers is the minimum input power required to initiate laser oscillation. It has been widely accepted that the conventional laser threshold occurring around a unity intracavity photon number can be eliminated in the input-output curve by making the so-called β parameter approach unity. The recent experiments, however, have revealed that even in this case the photon statistics still undergo a transition from coherent to thermal statistics when the intracavity mean photon number is decreased below unity. Since the coherent output is only available above the diminished threshold, the long-sought promise of thresholdless lasers to produce always coherent light has become questionable. Here, we present an always-coherent thresholdless laser based on superradiance by two-level atoms in a quantum superposition state with the same phase traversing a high-Q cavity. Superradiant lasing was observed without the conventional lasing threshold around the unity photon number and the photon statistics remained near coherent even below it. The coherence was improved by reducing the coupling constant as well as the excited-state amplitude in the superposition state. Our results pave a way toward always-coherent thresholdless lasers with more practical media such as quantum dots, nitrogen-vacancy centers and doped ions in crystals.
Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold ^{88}Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide ^{3}P_{1}→^{1}S_{0} intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth.
Sub-Natural Linewidth Superradiant Lasing with Cold 88^{88}88Sr Atoms
Superradiant lasers operate in the bad-cavity regime, where the phase coherence is stored in the spin state of an atomic medium rather than in the intracavity electric field. Such lasers use collective effects to sustain lasing and could potentially reach considerably lower linewidths than a conventional laser. Here, we investigate the properties of superradiant lasing in an ensemble of ultracold 88^{88}88Sr atoms inside an optical cavity. We extend the superradiant emission on the 7.5 kHz wide 3P1^3P_13P1​ →\rightarrow→ 1S0^1S_01S0​ intercombination line to several milliseconds, and observe steady parameters suitable for emulating the performance of a continuous superradiant laser by fine tuning the repumping rates. We reach a lasing linewidth of 820 Hz for 1.1 ms of lasing, nearly an order of magnitude lower than the natural linewidth
We consider a laser model consisting of a single four-level or three-level atom, an optical cavity, and an incoherent pump. Results for photon statistics for varying pump levels are obtained using a quantum trajectory algorithm. In particular, we calculate the mean photon number, Fano factor (which is the variance over the mean). We examine that the behavior of the single-atom device as \ensuremath{\beta}, the fraction of spontaneous emission into the lasing mode, is varied. Typical values considered for \ensuremath{\beta} are $0.01<\ensuremath{\beta}<1.0.$ We find that for large enough \ensuremath{\beta}, lasing action, with properties similar to those predicted by semiclassical theories that factorize atom-field correlations and use a small-noise approximation, can occur. Squeezing can occur as \ensuremath{\beta} is increased. There is no evidence of a sharp phase transition from weakly excited thermal light to coherent light at a particular pump power. This is consistent with work on many-atom lasers with \ensuremath{\beta} values in the range considered here. As \ensuremath{\beta} is increased, the output goes from quasithermal light to coherent and finally to squeezed light, progressing into a fully quantum-mechanical regime. We also consider the effects of cavity damping and spontaneous emission rates on these results.
Properties of a laser formed by a high-Q cavity and a single incoherently excited atom are studied on the basis of analytical solutions obtained for the quasi-probability P -function. Expressions for the boundaries separating various operating regimes of a one-atom laser (below threshold, above threshold, and self-quenching) are found. It is shown that lasing without inversion and lasing with the decay rate of the excited state exceeding the pump intensity are possible in the system. The degree of coherence of laser radiation is studied.