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Study of the refractometric stability of an interferometer equipment for gauge block calibration

We have developed an interferometer for gauge block calibration based on phase shifting evaluation. The measurement process can provide flatness, parallelism and longitude. The employed wavelengths need to be corrected according to the refractive index of the air the light beams passes through. In our case, this correction is obtained indirectly using readings of temperature, pressure and relative humidity taken by high resolution sensors. To preserve stability, the interferometer is encapsulated in a chamber with active temperature control. The design, measurement principle, calibration, stability and reproducibility are analyzed. Since one of our goals is to employ robust and cheap diode lasers as light sources, this paper describes also the system we are developing to carry out a red diode laser stabilization using a mode locking technique. The instruments and assembly employed to avoid the Doppler effect in the gas cells, which limit wavelength resolution, are described as well. Several experimental tests have been carried out that show the great susceptibility of this assembly to changes in environmental conditions, which affect the iodine cell's absorption spectrum.