<title>Use of electro-optical devices for optical path-length (OPL) compensation</title>

Abstract

We present the results of some laboratory experiments of the use of electro-optical (EO) devices to control the optical path length (OPL) of an interferometric array. One of the most important problems in interferometric beam combination is the control of the path length; this is coupled with the need for partial wavefront compensation in order to increase the sensitivity of the interferometer. Traditional approaches to such problems are often very expensive and sometimes impractical. For this reason we started an effort, both theoretically and experimentally, in order to investigate if less costly and more effective techniques can be applied. In our experiments we used single-cell LCDs in order to eliminate piston terms in a two- aperture interferometer. We used phase diversity techniques for extracting the phase information. Although the experimental results are still partial we believe that there is enough evidence that such devices can be used for the OPL control and partial wavefront compensation. Further testing is needed in order to assess the real capabilities of commercially available LCDs and the need, if any, of customization.