Abstract

Wavelength tunable laser diodes have recently been used for interferometric fringe stabilization and displacement measurement in the so-called active laser interferometers.¹ The basic idea is to compensate for any changes in the interference signal by tuning the frequency of the laser. A frequency- and amplitude-stabilized Zeeman He–Ne laser² is used instead in this work. Utilizing the extreme narrow linewidth (<1 MHz) of the laser, we have demonstrated that subnanometer resolution in the measurement of the displacement of a piezoelectric transducer is possible. While the single-mode tuning range of the laser is only ~300 MHz, displacement measurements over many wavelengths can be realized by adjusting the optical path length difference of the two arms of the Michelson interferometer. Interferometric fringe stabilization has also been realized with a stabilization factor of more than 2 orders of magnitude.

© 1988 Optical Society of America