We present a description of a system for automatic alignment of optical interferometers. The technique relies on using differential phase modulation to permit the detection of the phase difference between two fundamental-mode Gaussian beams at the output of an interferometer. Measurements of the spatially varying phase difference between the two beams by use of one or more multielement photodiodes permits information to be derived about the mismatch in overlap between the phase fronts at the output of the interferometer.

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.

We present a description of the prototype interferometric gravitational wave detector at Glasgow. The detector, which has been under development for a number of years, consists of two perpendicular 10-m-long high finesse Fabry–Perot cavities formed between test masses hung as pendulums and is illuminated with a cw argon ion laser. The differential displacement sensitivity of the detector is ∼7×10−19 m/√Hz from 500 Hz → 3 kHz and is close to being limited by photoelectron shot noise in the detected photocurrent.

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This paper describes some of the design aspects of a prototype high-speed stylus profilometer intended primarily for rapid 3D measurement of small surface areas.