Standing Wave Interferometer with Stabilization of Wavelength on Air

We present an experimental arrangement of an interferometric system designed to operate with full compensation for varying refractive index of air in the measuring axis. The concept is based on a principle where the wavelength of the laser source is derived not from an optical frequency of the stabilized laser but from a fixed length being a baseplate or a frame of the whole measuring setup. This results into stabilization of the wavelength of the laser source in atmospheric conditions to mechanical length of suitable etalon made of a material with very low thermal expansion. The ultra-low thermal expanding glass ceramic materials available on the market perform thermal expansion coefficients on the level 10(-8) which significantly exceeds the limits of uncertainty posed by indirect evaluation of refractive index of air through Edlen formula. This approach represents a contribution primarily to high-resolution and high-precision dimensional metrology in the nanoscale.