Spatial Interference: From Coherent To Incoherent

TL;DR

This paper demonstrates that interference patterns can be formed using spatially incoherent light sources by summing many fluctuating sample patterns, enabling holography without coherent sources.

Contribution

It introduces a novel interference scheme using incoherent light sources that produces hologram-like patterns, expanding applications to incoherent sources like x-ray and electron beams.

Findings

Interference patterns emerge from incoherent sources when summing multiple sample patterns.

The method reproduces hologram information using incoherent light, similar to coherent holography.

Potential applications include holography with x-ray and electron sources.

Abstract

It is well known that direct observation of interference and diffraction pattern in the intensity distribution requires a spatially coherent source. Optical waves emitted from portions beyond the coherence area possess statistically independent phases, and will degrade the interference pattern. In this paper we show an optical interference experiment, which seems contrary to our common knowledge, that the formation of the interference pattern is related to a spatially incoherent light source. Our experimental scheme is very similar to Gabor's original proposal of holography[1], just with an incoherent source replacing the coherent one. In the statistical ensemble of the incoherent source, each sample field produces a sample interference pattern between object wave and reference wave. These patterns completely differ from each other due to the fluctuation of the source field distribution. Surprisingly, the sum of a great number of sample patterns exhibits explicitly an interference pattern, which contains all the information of the object and is equivalent to a hologram in the coherent light case. In this sense our approach would be valuable in holography and other interference techniques for the case where coherent source is unavailable, such as x-ray and electron sources.