High-luminosity high-resolution interferometer for measurement of coherence of optical radiation

A description is given of an interferometer intended for measurements of small spatial coherence radii. This instrument has several advantages over the Young and Mach–Zehnder interferometers, which are also used for this purpose. The results are reported of measurements of the spatial correlation functions of the radiation emitted by a helium–neon laser and an yttrium aluminum garnet (YAG) laser. A study of the latter laser under multimode operation conditions indicated that the coherence radius was ~0.1 mm for a beam of 5 mm radius.