Experiments on Superfluorescence in Cesium
Superfluorescence (SF), i.e., the cooperative or superradiant emission of an initially inverted system, has been the subject of extensive theoretical investigation[2–9]. The first experiment and its interpretation have aroused further interest in the phenomenon. The SF decay of a pencil-shaped volume of density n is characterized by the emission of a delayed pulse (or pulses) in a narrow cone along the sample axis; the delay time τD is nearly proportional to n−1, the peak power is nearly proportional to n2. The quantitative description of the initial generation of atomic coherence and of the subsequent coherent pulse evolution is still under discussion and so are the precise conditions for SF to occur. Stringent conditions have been specified by Bonifacio and Lugiato for what these authors call “pure SF”: (a) a pure two-level system, (b) a pencil-shaped volume of Fresnel number N ≡ A/λL = 1, (c) transverse excitation with a pump pulse of duration τp ≫ τD, and (d) τE < τC < τR < τD < T1, T’2, T*2.
Unable to display preview. Download preview PDF.
- 3.R. Bonifacio, P. Schwendimann, and F. Haake, Phys. Rev. A4, 302 and 854 (1971).Google Scholar
- 6.R. Bonifacio and L.A. Lugiato, Phys. Rev. All, 1507 (1975) and 12, 587 (1975).Google Scholar
- 7.E. Ressayre and A. Tallet, Phys. Rev. Lett. 37, 424 (1976); C.T. Lee, Phys. Rev. A14, 1926 (1976).Google Scholar
- 8.R. Friedberg and S.R. Hartmann, Phys. Lett. 37A, 285 (1971), and Phys. Rev. A13, 495 (1976).Google Scholar
- 10.N. Skribanowitz, I.P. Herman, J.C. MacGillivray, and M.S. Feld, Phys. Rev. Lett. 30, 309 (1973); I.P. Herman, J.C. MacGillivray, N. Skribanowitz and M.S. Feld, in Laser Spectroscopy, R.G. Brewer and A. Mooradian, editors ( Plenum, NY, 1974 ).Google Scholar
- 12.The shape-factor can be written as µ = ξ(3λ2/87A). For.N » 1 the parameter is constant, ξ = 1, so that TR = (8Πt3Ln). For N = ξ is calculated from ref. 4, eq. (5.16). The result is = 0.48, 0.67, 0.79, 0.85, 0.86, and 0.90 for L = 0.5, 1.0, 2.0, 3.0, 5.0 and 10.0 cm. In view of the unavoidable experimental uncertainty in N the value ξ = 1 is used throughout in this paper.Google Scholar
- 13.a) H.M. Gibbs in Proceedings of the leeting on Cooperative Effects,Redstone Arsenal, December 1976, C.M. Bowden, D. Howgate, and H. Robl, editors, (Plenum, NY, 1977); (b) Q.H.F. Vrehen, ibidem.Google Scholar
- 18.J.C. MacGillivray, private communication.Google Scholar