Heterodyne Standing-Wave Interferometer with Improved Phase Stability

Abstract This paper describes a standing-wave interferometer with two laser sources of different wavelengths, diametrically opposed and emitting towards each other. The resulting standing wave has an intensity profile which is moving constant velocity, directly detected inside the beam by thin transparent photo sensors. first sensor at fixed position, serving as phase reference for second one moved along optical axis, in frequency shift, proportional to velocity. difference between both sensors evaluated purpose interferometric length measurements.