Spontaneous emission in a micro optical cavity from spectrally broadened atoms

Arup Banerjee

Kikuo Ujihara

In this chapter, the authors develop a consistent theory of spontaneous emission in an optical micro cavity from a broadened atom. They derive the atomic broadening from first principles by assuming the presence of reservoirs coupled to the atoms. The simplest model of the atom is the so-called two-level atom, which has only two energy levels, the excited and the ground level. However, realistic atoms are surrounded by media that affect the atoms, giving them homogeneous or inhomogeneous broadening. The important parameter of coupling ratio of spontaneous emission to a desired quasi mode cannot be exactly treated by the present mathematical model of the cavity, although it is easily seen qualitatively that the ratio will decrease with increasing atomic broadening. The authors assume that each atom emits independently and ignored the possible interaction among atoms during spontaneous emission. Solving the master equation for the density matrix elements, the readers have derived formulas for spontaneous emission rate and emission spectrum.

JOSIP SEKE

Yun‐Jie Xia, Guang-Can Guo, P. T. Leung

We consider the spontaneous emission of a broadening molecule on the surface of a micro-sphere in this paper. The density of states for the micro-cavity is derived from quasi-normal models(QNM's) expansion of the correlation functions of electromagnetic fields. Through detailed analysis we show that only weak coupling between a broadening atom(molecule) and the electromagnetic fields exists in a dielectric sphere cavity whether the sphere is small or big. From these results we find the explicit expression of the spontaneous emission decay rate for a surfactant broadening molecule on the surface of a micro-droplet with radius $a$, in which only $1/a$ and $1/a^{2}$ components exhibit. Then we apply this expression to a real experiment and obtain a consistent result with the experiment. We also show that the real-cavity model of local field correction is accurate, and reveal that the local-field correction factor can be measured precisely and easily by fluorescence experiments of surfactant molecules. Moreover, the spontaneous decay of a surfactant molecular on droplet's surface is sensitive to the atomic broadening, so that the fluorescence experiment in a micro-sphere cavity can be used to estimate the radiative broadening.

Akiyoshi Takada, Kikuo Ujihara

Yann G. Boucher, Yannick Dumeige, Patrice Féron

Exploiting the formal analogy between the transfer function of a micro-resonator and the optical susceptibility of an atomic medium, we investigate the spectral and energetic properties of active cavities seen as mesoscopic "photonic atoms". The resemblance is not limited to linear regime; a structural equivalent can be found for such fundamental processes as spontaneous emission, stimulated absorption and emission, saturation of the active medium or induced transparency.