Spatial Coherence Spectroscopy and Its Applications

Discovery of the Wolf effect [1-4], i.e. frequency change due to the source correlations during the propagation of radiation and its subsequent verifieation by experiments [5-8] have been a subject of great inleresl in the past few years. Since the discovery of this effect, several investigations have been made in different areas of modern optics. This effect has aiso attracted great interest in interference experiments [9-11] with partially coherent broad bandwidth light. It has been shown that the state of coherence of ihe incident wave field over the plane of the double slit in Young’s interference experiment leads to spectral changes in the region of superposition and the superposed spectrum shows a shift in the central frequency for a narrow band light and spectral modulations for a broad band light. Experimental confirmation [12-13] of these theoretical predictions have already been made. It has also been shown thal two beam interference in a Mach-Zehnder inlerferometer results in spectral changes in the form of spectral modulations in-the superposed spectrum. Some applicutions [14-19] of these studies in various mcasurements are disenssed in detail.