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Mechanical stabilization of a gas laser interferometric system for making diffractive lenses

It may happen that when mounting a large interferometric system as a holographic system the diffraction efficiency achieved results less than expected. If our holographic film was checked with more stable systems and the laser we employ has enough short bandwidth as to guarantee coherence at the path difference, then we must attribute the problem to instabilities. These may be: on the wavelength or mechanically inside the laser, on temperature of the air or mechanical vibrations on the holders. Mechanical vibrations may be external to the laboratory and difficult to control but a simple method consists in making rigid connections by metal bars on the upper part of the supporting elements. It may seem too complicated but is more effective and certainly cheaper than employing specially designed dumping tables. We will describe our results on making large holographic diffractive lenses on systems larger than 3 m x 3 m. Introduction When using large interferometric systems problems with instabilities are commonly found. In holographic systems, this instabilities result in loss of the diffraction efficiency. Many works were published to reduce the instability by means of active elements requiring electronics 2 . We develop a simple method that consists in making rigid connections by metal bars on the upper part of the supporting elements. In this paper we show how to perform the method and the improve of the diffraction efficiency after the use of it.