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Absolute Distance Measurements with Tunable Semiconductor Laser

The work is oriented to development of an absolute distance interferometer with a narrow-linewidth tunable VCSEL laser (Vertical-Cavity Surface-Emitting Laser) at 760 nm and a wavelength-scanning interferometry technique improved by an amplitude division of interference fringe [Xiaoli D et al, Meas. Sci. Technol. 9 1031 (1998); Creath K Appl. Opt. 26 2810 (1987)]. This laser performs the mod-hop free tuning range up to 1.4 nm and the value of the injection current controls the wavelength. With respect to the high sensitivity of the emitted wavelength to injection current fluctuations, we provided stabilization of laser frequency by means of an electronic frequency lock to modes of the Fabry-Perot glass etalon. Instantaneous values of the interference phase before and after the scanning process are recorded for a longer interval due to data averaging. For the first laboratory experiments, we have measured preliminary results with relative uncertainty of absolute distance measurement at 8 × 10-5 level.