Improved Version of a Polarized Beam Heterodyne Interferometer

Abstract

The heterodyne interferometer is a very sensitive instrument with a wide dynamic range, suitable for measuring surface displacements of amplitude down to mented present some disadvantages. T heir optical mounting is space demanding and alignments are critical. In addition, some inherent instabilities have also been identified. We have constructed a new version of the instrument which considerably reduces these disadvantages. The combination of a colinear beam Bragg cell and of a polarizing beam splitter makes the optical arrangement compact (less than lOcm long) and simplifies the alignment p rocedure. Ekper*pental results show that the sensitivity, lo+ A/ &z,reaches the t heoretical value and that the instabilities a re reduced by more than one order of magnitude, down to 0.3% of the output signal. 1. However, the interferometers p resently imple