Spontaneous emission of coherent light in highly excited media

Mário G. Silveirinha

H. Maeda, Avigail Yariv

Roy J. Glauber

Mikael Afzelius, M. U. Staudt, Hugues de Riedmatten +6 more

We report an interference experiment of spontaneous emission of light from two distant solid-state ensembles of atoms that are coherently excited by a short laser pulse. The ensembles are erbium ions doped into two LiNbO 3 crystals with channel waveguides, which are placed in the two arms of a Mach–Zehnder interferometer. The light that is spontaneously emitted after the excitation pulse shows first-order interference. By a strong collective enhancement of the emission, the atoms behave as ideal two-level quantum systems and no which-path information is left in the atomic ensembles after emission of a photon. This results in a high fringe visibility of 95%, which implies that the observed spontaneous emission is highly coherent.

P. Schwendimann

Vadim A. Alekseev

To extend the capabilities of the existing spectroscopic methods of investigation and diagnostics of gaseous media, we consider a macroscopic effect of an increase in the rate of spontaneous emission, which results in the transition of a considerable part of excited molecules to lower-lying optically accessible states with light pulse emission along the direction of propagation of the exciting laser radiation. As an application of the effect of amplified spontaneous emission, we propose the population with its help of optically inaccessible electronic states of atoms and molecules.