The measurement of phase through the propagation of intensity: an introduction

Abstract

The concept of phase is deeply instilled in the mind of every physics student from a very early age and its measurement seems inevitably intertwined with the need to perform interferometry. More recently, a number of important phase visualisation and measurement techniques have emerged that do not require interference. This paper introduces the concept of phase by treating it as a potential that determines the flow of energy, which leads to the idea that phase can be measured by observing the evolution of the intensity of the light on propagation. The ideas have found application in a number of areas, including optical, X-ray, neutron and electron imaging physics and these are explained.

Keywords:

• intensity
• phase
• coherence
• imaging
• inverse problems
• X-rays
• synchrotrons

Acknowledgements

The author acknowledges the support of the Australian Research Council through its Fellowship and Centres of Excellence schemes.