Two-photon emission and absorption in the presence of a thermalized electromagnetic field

N. A. Enaki, DUMITRU BOGDAN MIHALACHE

N. A. Enaki, O. B. Prepelitsa

N. A. Enaki, M. A. Makovei

We study the cooperative two-photon spontaneous decay of an excited atomic system in a microcavity whose size is of the order of several wavelengths of atomic radiation. We show that a thermalized electromagnetic field in the microcavity strongly affects the two-photon cooperative spontaneous emission of radiation. The increase in the rate of spontaneous cooperative decay is due to the presence of a small number of thermalized photons in a microcavity mode. At low temperatures, the two-photon absorption probability is found to be a linear function of the two-photon flux, and photon superbunching is observed.

S. N. Biswas, S. N. Haque, Man Mohan

Two-Raman-photon emission in hydrogen atoms in the presence of an intense electromagnetic field has been calculated utilizing the method of Dalgarno and Lewis. We give a general formulation for ($n\ensuremath{-}2$)-photon absorption and two-photon emission and also give numerical results for two-photon emission in the $1s\ensuremath{-}2p$ transition in hydrogen atoms. It is found that the emission of two spontaneous Raman photons could become important when the energy of the intense photon approaches the ionization energy. Finally, in the spectrum of the emitted Raman photon, faint lines are expected corresponding to the resonant peaks in the cross section.

F.F. Körmendi

P.V. Landshoff, Allen Metherell, Gareth Rees

Radiative transitions When a system changes its energy as the result of the emission or the absorption of a photon, it is said to undergo radiative transition. There are three kinds of radiative transition. In the presence of an electromagnetic field the system can absorb a photon, so that its energy is raised to a higher level. If the system is initially in a state other than the ground state, it can emit a photon and so shed energy. This can happen without the presence of any external electromagnetic field, in which case a spontaneous emission is said to occur. On the other hand, if the excited system is placed in an electromagnetic field that varies in time with the appropriate frequency, the probability that it will emit a photon can be greatly enhanced. In this case the emission process is known as stimulated emission . Stimulated emission is the basis of maser and laser action, which we describe in this chapter. First, we construct a simple model that allows us to investigate how the internal structure of a quantum system changes as the result of a radiative transition. Although the model is very simple, it will allow us to understand the main features of the proper, more exact treatment. We shall deal mainly with absorption and stimulated emission, the two types of radiative transition where there is an external electromagnetic field.