Experimental demonstration of an automatic alignment system for optical interferometers

An automatic alignment system, based on a differential phase-sensing technique described in a companion paper [Appl. Opt.33, 0000, (1994)], has been experimentally demonstrated on the 10-m prototype laser interferometric gravitational wave detector in Glasgow. The alignment system developed was used to control the orientations of two mirrors in a 10-m-long suspended Fabry-Perot cavity with respect to the direction defined by the input laser beam. The results of the test and a discussion of the performance of the system are given.