Enhancement of spontaneous and stimulated emission in the microlaser by standing-wave resonant excitation

Abstract
By a new method of momentum–space excitation an increase of the spontaneous emission rate and a large reduction of the microlaser threshold are obtained. The method is demonstrated by an optically excited micro-laser filled with europium atoms. The method is general and may be extended to active cavities with any dimension and geometry. Our results on spontaneous emission are interpreted as a demonstration of the first-order interference of the vacuum field.