Superfluorescence
Author: the photonics expert Dr. Rüdiger Paschotta (RP)
Definition: collective emission of radiation by an ensemble of excited atoms or ions
- luminescence
- fluorescence
- parametric fluorescence
- superfluorescence
- superluminescence
- fluorescence
Related: superradiancesuperluminescencefluorescencespontaneous emissionamplified spontaneous emissionstimulated emissionquantum optics
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DOI: 10.61835/9i9 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn
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What is Superfluorescence?
Superfluorescence is a phenomenon of quantum optics. It is the collective emission of fluorescent light by an ensemble of excited atoms or ions [1]. Initially, the atoms (or ions) are incoherently excited (e.g. by optical pumping), so that there is no macroscopic dipole moment. The process starts slowly with spontaneous emission. The radiation field then couples the radiation phases of the different atoms, so that they become synchronized, and a collective emission releases the stored energy as a superfluorescent pulse. The pulse maximum occurs after some delay, and the pulse duration can be short compared with the upper-state lifetime of a single atom. The maximum intensity of the emitted light scales with the square of the number of atoms.
Superfluorescence is similar to superradiance, but in the latter case there is a macroscopic dipole moment from the beginning, created by the excitation process: the excitation is created with a light pulse such that all involved atoms have about the same location on the Bloch sphere. (The intensity must be sufficiently uniform, and the involved atoms should behave all in the same way, e.g. not influenced by locally varying conditions.) Unfortunately, however, many authors do not distinguish between superfluorescence and superradiance.
The phenomenon of superfluorescence, as defined above, is also substantially different from superluminescence or amplified spontaneous emission (ASE). The latter process does not require close proximity and coherent excitation, and is based only on fluorescence and stimulated emission. Superfluorescence and superluminescence are processes which can compete in certain situations, depending on, e.g., the dephasing rate of the atomic system [4]. In laser amplifiers, that dephasing is often too fast to allow for anything like superfluorescence.
Unfortunately, there appears to be no authoritative definition of the term superfluorescence, and the literature contains many scientific papers where the term has been used with different meanings. For example, the term superfluorescence source (or superfluorescent source) is in most cases used such that it means the same as the actually more suitable term superluminescent source.
Frequently Asked Questions
This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).
What is superfluorescence?
Superfluorescence is the collective emission of fluorescent light from an ensemble of initially incoherently excited atoms. The radiation field synchronizes the optical phases of the emitters, leading to a short, intense pulse of light with a peak intensity proportional to the square of the number of atoms.
What is the difference between superfluorescence and superradiance?
In superfluorescence, the atoms are initially excited incoherently, with no macroscopic dipole moment. In superradiance, the excitation process itself creates a macroscopic dipole moment from the start, meaning the atoms are already coherently prepared.
How does superfluorescence differ from superluminescence?
Superfluorescence is a coherent, collective process where atoms synchronize their emission phase. In contrast, superluminescence (or amplified spontaneous emission) is based on stimulated emission amplifying spontaneous emission and does not involve such phase synchronization between the emitting atoms.
Is a 'superfluorescence source' the same as a superluminescent source?
Although the term 'superfluorescence source' is often used, it is typically a misnomer for what is more accurately called a superluminescent source. The underlying physical principles of superfluorescence and superluminescence are different.
Bibliography
| [1] | R. Bonifacio and L. A. Lugiato, “Cooperative radiation processes in two-level systems: superfluorescence”, Phys. Rev. A 11 (5), 1507 (1975); doi:10.1103/PhysRevA.11.1507 |
| [2] | R. Bonifacio and L. A. Lugiato, “Cooperative radiation processes in two-level systems: superfluorescence. II”, Phys. Rev. A 12 (2), 587 (1975); doi:10.1103/PhysRevA.12.587 |
| [3] | M. S. Malcuit et al., “Transition from superfluorescence to amplified spontaneous emission”, Phys. Rev. Lett. 59 (11), 1189 (1987); doi:10.1103/PhysRevLett.59.1189 |
| [4] | J. J. Maki et al., “Influence of collisional dephasing processes on superfluorescence”, Phys. Rev. A 40 (9), 5135 (1989); doi:10.1103/PhysRevA.40.5135 |
| [5] | G. Findik et al., “High-temperature superfluorescence in methyl ammonium lead iodide”, Nature Photonics 15, 676 (2021); doi:10.1038/s41566-021-00830-x |
| [6] | K. Huang et al., “Room-temperature upconverted superfluorescence”, Nature Photonics 16, 737 (2022); doi:10.1038/s41566-022-01060-5 |
(Suggest additional literature!)
2024-03-18
Is there a difference between superfluorescent coherent emission and laser radiation or ASE?
The author's answer:
Absolutely. In lasers or ASE sources, the conditions for superfluorescence are generally not fulfilled; we have too fast dephasing of the laser ions.