Interference Fringes Produced by Superposition of Two Independent Maser Light Beams

George Magyar, L. Mandeļ

R. L. Pfleegor, L. Mandeļ

Interference fringes produced by the superposition of light beams from two independent lasers have been investigated under conditions where the light flux was so low that one photon was usually received at the detector before the next one was emitted by one or the other source. Because the average number of photons detected in each observation was only about 10, a photon correlation technique was used to demonstrate the presence of interference fringes. The measurement procedure was automated, and this led to much greater statistical accuracy than was previously reported. The effect of varying the observation time and the number of interference fringes sampled was investigated, and found to be in good agreement with theory.

R.L. Bailey, J. H. Sanders

Todorka L. Dimitrova, Antoine Weis

A new lecture demonstration experiment for illustrating the wave-particle dualism of light is proposed. The equipment is based on the interference of two coherent light beams produced in a Mach-Zehnder interferometer. Light from a green laser pointer is used to perform two simultaneous experiments. The expanded laser beam traverses a Mach-Zehnder interferometer, which allows one to create a superposition of two coherent beams and to adjust the period of their interference fringes in a simple way—a didactic tool to illustrate the wave nature of light. The main feature of the experiment is the use of the same equipment to demonstrate the particle nature of light. For this the entering beam is strongly attenuated and photons at the exit of the interferometer are detected by a photomultiplier (PM) with a narrow slit, connected to a speaker. We propose a realization in which both of these experiments can be demonstrated simultaneously. Special design criteria of the set-up are its low cost, its simplicity, its didactical power and its suitability for large lecture halls.

Yoh‐Han Pao

R. L. Pfleegor, L. Mandeļ

Interference effects produced by the superposition of the light beams from two independent single-mode lasers have been investigated experimentally. It is found that interference takes place even under conditions in which the light intensities are so low that, with high probability, one photon is absorbed before the next one is emitted by one or the other source. Since the average number of registered photons per trial was only about 10, photon correlation techniques were required to demonstrate the interference. The interpretation of the experiment, and the question whether it demonstrates interference between two photons, are discussed.