Interferometer for use in wave-front testing with a cross slit

A simple and novel interferometric setup for wave-front testing that uses a cross slit is described. In this method, the test beam illuminates a cross slit placed at the front focal plane of a Fourier lens. It selects two ort hogonal slices from the test beam, and the interference of these two beams is observed at a slightly defocused plane near the back focal plane. Fringe s of different conical forms (circular, elliptical, or hyperbolic) so obtai ned can be used for testing a coherent wave front in general. The theory, s upported by some experimental results, is presented. An application of the method to the study of the nature of asymmetry in the beam profile of a sem iconductor diode laser beam is demonstrated. (C) 2000 Optical Society of Am erica OCIS codes: 120.2650, 120.3180.