Near-field phase measurements of diode laser arrays

We have developed a self-referencing interferometer that will allow phase measurements of the near field of diode arrays. The method uses a double-slit aperture that is scanned across a magnified image of the diode near field. The far-field double-slit fringe locations then give a direct measurement of the phase difference between the two slits. We can then reconstruct the phase using the sampled difference data. The method has several advantages over other interferometric techniques including (1) the wavefront is interfered with itself, so that a separate reference wavefront is not needed; (2) the method is insensitive to array near-field intensity variations so that fringe maps need not be deconvolved from intensity variations; (3) the method works well in the presence of broadband radiation. The source needs very little coherence length which is quite an important consideration for diode lasers. Data from several commercially available devices are presented. (Poster paper)