Experimental Observation of Invariance of Spectral Degree of Coherence with Change in Bandwidth of Light

TL;DR

This study experimentally demonstrates that the spectral degree of coherence of light remains invariant despite changes in the light's bandwidth, using a Young's interferometer setup with variable bandwidth sources.

Contribution

It provides experimental evidence that the spectral degree of coherence does not depend on the bandwidth of the light source, challenging assumptions about bandwidth effects.

Findings

Spectral degree of coherence remains unchanged with bandwidth variation

Interference fringe visibility is unaffected by bandwidth changes

Experimental validation using a polychromatic source and monochromator

Abstract

An experimental study is conducted to show the effect of the change in bandwidth of light on the spectral degree of coherence at a pair of points in the cross-section of a beam. For this purpose a polychromatic source and a monochromator with variable entrance and exit slits were used to produce a variable bandwidth source. The classic Youngs interferometer was used to produce an interference pattern. The spectral measurements of the visibility of the interference fringes show that the spectral degree of coherence remains unaffected by the change in the frequency pass-band of the light.