Optical EngineeringNew diode laser light source for absolute ranging two-wavelength interferometry
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Two-wavelength interferometry is a well-known technique to enlarge the ambiguity range of conventional interferometric ranging systems. The main problem with this technique is that the light source used must generate the desired wavelengths, which must be adaptable to the actual application. Those wavelengths have to be known precisely and must be stabilized to the desired accuracy. Because of the lack of an inexpensive, compact, and intense light source that provides for the desired wavelengths, two-wavelength ranging systems previously have been without technical importance. We present a new light source for this purpose, which is based on stabilized semiconductor lasers. Our system generates two stabilized wavelengths in the submicrometer range and a synthetic wavelength in the submillimeter range, respectively. In the case of the submillimeter wavelength, both laser wavelengths are locked to the same Fabry-Pérot resonator. This method, previously known in principle, is used for semiconductor lasers for the first time.