Center for Applied Physics and Astronomical Research Tabriz university- Tabriz -Iran

By using new theoretical point of view on cross- spectral density function of the field, the propagation of partially coherent beam produce by a plane source is investigated. Then we show, experimentally, the coherence length in the source plane can be measured directly from the far zone intensity distribution. The effects of the size and coherence of the source on beam directionality will be discussed. Our experimental results will be compared with the special case when the beam is the Gaussian Schell-Model type and it is shown that our prediction has a good agreement.