The following article describes the realization of a laser without any external resonance structure and the behaviour of the emitted radiation.
The experimental setup consits of a discharge tube closed with Brewster windows and the excitation electronics.
The excitation process which brings the atoms to the upper laser level (2 p6 Neon) will not establish any coherence between the atoms.
Space coherence of the radiation has its origin in the correlated behaviour of the radiating atoms.
Theoretical and experimental values of the fringe visibility are in close agreement for a path difference till to 440 cm, if temporal coherence is measured in an MICHELSON experiment. Interference fringes result if the radiation emerging from both sides of the tube is superimposed. The contrast decreases rapidly with the number of radiation pulses producing the interference pattern.